[MM-48528] Add support for SendGrid X-SMTPAPI header in email sends (#22296)

* Add support for SendGrid X-SMTPAPI header for categorizing sent emails to track performance

* Implement feedback

* Remove unnecessary struct

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

app/admin.go

@@ -195,7 +195,7 @@ func (a *App) TestEmail(userID string, cfg *model.Config) *model.AppError {
 	T := i18n.GetUserTranslations(user.Locale)
 	license := a.Srv().License()
 	mailConfig := a.Srv().MailServiceConfig()
-	if err := mail.SendMailUsingConfig(user.Email, T("api.admin.test_email.subject"), T("api.admin.test_email.body"), mailConfig, license != nil && *license.Features.Compliance, "", "", "", ""); err != nil {
+	if err := mail.SendMailUsingConfig(user.Email, T("api.admin.test_email.subject"), T("api.admin.test_email.body"), mailConfig, license != nil && *license.Features.Compliance, "", "", "", "", ""); err != nil {
 		return model.NewAppError("testEmail", "app.admin.test_email.failure", map[string]any{"Error": err.Error()}, "", http.StatusInternalServerError)
 	}
 

app/admin_advisor.go

@@ -194,7 +194,7 @@ func (a *App) NotifyAndSetWarnMetricAck(warnMetricId string, sender *model.User,
 				return model.NewAppError("NotifyAndSetWarnMetricAck", "api.email.send_warn_metric_ack.failure.app_error", map[string]any{"Error": err.Error()}, "", http.StatusInternalServerError)
 			}
 
-			if err := mail.SendMailUsingConfig(model.MmSupportAdvisorAddress, subject, body, mailConfig, false, "", "", "", sender.Email); err != nil {
+			if err := mail.SendMailUsingConfig(model.MmSupportAdvisorAddress, subject, body, mailConfig, false, "", "", "", sender.Email, "NotifyAndSetWarnMetricAck"); err != nil {
 				return model.NewAppError("NotifyAndSetWarnMetricAck", "api.email.send_warn_metric_ack.failure.app_error", map[string]any{"Error": err.Error()}, "", http.StatusInternalServerError)
 			}
 		}

app/email/email.go

@@ -27,6 +27,15 @@ import (
 
 const serverInactivityHours = 100
 
+// Returns category if enabled is true (default false)
+// If "" is returned when enabled is false, the category headers aren't attached to the email
+func getSendGridCategory(category string, enabled bool) string {
+	if enabled {
+		return category
+	}
+	return ""
+}
+
 func (es *Service) SendChangeUsernameEmail(newUsername, email, locale, siteURL string) error {
 	T := i18n.GetUserTranslations(locale)
 
@@ -46,7 +55,7 @@ func (es *Service) SendChangeUsernameEmail(newUsername, email, locale, siteURL s
 		return err
 	}
 
-	if err := es.sendMail(email, subject, body); err != nil {
+	if err := es.sendMail(email, subject, body, "ChangeUsernameEmail"); err != nil {
 		return err
 	}
 
@@ -79,7 +88,7 @@ func (es *Service) SendEmailChangeVerifyEmail(newUserEmail, locale, siteURL, tok
 		return err
 	}
 
-	if err := es.sendMail(newUserEmail, subject, body); err != nil {
+	if err := es.sendMail(newUserEmail, subject, body, "EmailChangeVerifyEmail"); err != nil {
 		return err
 	}
 
@@ -105,7 +114,7 @@ func (es *Service) SendEmailChangeEmail(oldEmail, newEmail, locale, siteURL stri
 		return err
 	}
 
-	if err := es.sendMail(oldEmail, subject, body); err != nil {
+	if err := es.sendMail(oldEmail, subject, body, "EmailChangeEmail"); err != nil {
 		return err
 	}
 
@@ -143,7 +152,7 @@ func (es *Service) SendVerifyEmail(userEmail, locale, siteURL, token, redirect s
 		return err
 	}
 
-	if err := es.sendMail(userEmail, subject, body); err != nil {
+	if err := es.sendMail(userEmail, subject, body, "VerifyEmail"); err != nil {
 		return err
 	}
 
@@ -168,7 +177,7 @@ func (es *Service) SendSignInChangeEmail(email, method, locale, siteURL string)
 		return err
 	}
 
-	if err := es.sendMail(email, subject, body); err != nil {
+	if err := es.sendMail(email, subject, body, "SignInChangeEmail"); err != nil {
 		return err
 	}
 
@@ -226,7 +235,7 @@ func (es *Service) SendWelcomeEmail(userID string, email string, verified bool,
 		return err
 	}
 
-	if err := es.sendMail(email, subject, body); err != nil {
+	if err := es.sendMail(email, subject, body, "WelcomeEmail"); err != nil {
 		return err
 	}
 
@@ -259,11 +268,11 @@ func (es *Service) SendCloudUpgradeConfirmationEmail(userEmail, name, date, loca
 	}
 
 	if isYearly {
-		if err := es.SendMailWithEmbeddedFilesAndCustomReplyTo(userEmail, subject, body, *es.config().SupportSettings.SupportEmail, embeddedFiles); err != nil {
+		if err := es.SendMailWithEmbeddedFilesAndCustomReplyTo(userEmail, subject, body, *es.config().SupportSettings.SupportEmail, embeddedFiles, "CloudUpgradeConfirmationEmail"); err != nil {
 			return err
 		}
 	} else {
-		if err := es.sendEmailWithCustomReplyTo(userEmail, subject, body, *es.config().SupportSettings.SupportEmail); err != nil {
+		if err := es.sendEmailWithCustomReplyTo(userEmail, subject, body, *es.config().SupportSettings.SupportEmail, "CloudUpgradeConfirmationEmail"); err != nil {
 			return err
 		}
 	}
@@ -304,7 +313,7 @@ func (es *Service) SendCloudWelcomeEmail(userEmail, locale, teamInviteID, workSp
 		return err
 	}
 
-	if err := es.sendEmailWithCustomReplyTo(userEmail, subject, body, *es.config().SupportSettings.SupportEmail); err != nil {
+	if err := es.sendEmailWithCustomReplyTo(userEmail, subject, body, *es.config().SupportSettings.SupportEmail, "CloudWelcomeEmail"); err != nil {
 		return err
 	}
 
@@ -330,7 +339,7 @@ func (es *Service) SendPasswordChangeEmail(email, method, locale, siteURL string
 		return err
 	}
 
-	if err := es.sendMail(email, subject, body); err != nil {
+	if err := es.sendMail(email, subject, body, "PasswordChangeEmail"); err != nil {
 		return err
 	}
 
@@ -355,7 +364,7 @@ func (es *Service) SendUserAccessTokenAddedEmail(email, locale, siteURL string)
 		return err
 	}
 
-	if err := es.sendMail(email, subject, body); err != nil {
+	if err := es.sendMail(email, subject, body, "UserAccessTokenAddedEmail"); err != nil {
 		return err
 	}
 
@@ -385,7 +394,7 @@ func (es *Service) SendPasswordResetEmail(email string, token *model.Token, loca
 		return false, err
 	}
 
-	if err := es.sendMail(email, subject, body); err != nil {
+	if err := es.sendMail(email, subject, body, "PasswordResetEmail"); err != nil {
 		return false, err
 	}
 
@@ -415,7 +424,7 @@ func (es *Service) SendMfaChangeEmail(email string, activated bool, locale, site
 		return err
 	}
 
-	if err := es.sendMail(email, subject, body); err != nil {
+	if err := es.sendMail(email, subject, body, "MfaChangeEmail"); err != nil {
 		return err
 	}
 
@@ -501,7 +510,7 @@ func (es *Service) SendInviteEmails(
 				mlog.Error("Failed to send invite email successfully ", mlog.Err(err))
 			}
 
-			if err := es.sendMail(invite, subject, body); err != nil {
+			if err := es.sendMail(invite, subject, body, "InviteEmail"); err != nil {
 				mlog.Error("Failed to send invite email successfully ", mlog.Err(err))
 				if errorWhenNotSent {
 					return SendMailError
@@ -617,7 +626,7 @@ func (es *Service) SendGuestInviteEmails(
 				mlog.Error("Failed to send invite email successfully", mlog.Err(err))
 			}
 
-			if nErr := es.SendMailWithEmbeddedFiles(invite, subject, body, embeddedFiles, "", "", ""); nErr != nil {
+			if nErr := es.SendMailWithEmbeddedFiles(invite, subject, body, embeddedFiles, "", "", "", "InviteEmail"); nErr != nil {
 				mlog.Error("Failed to send invite email successfully", mlog.Err(nErr))
 				if errorWhenNotSent {
 					return SendMailError
@@ -765,7 +774,7 @@ func (es *Service) SendInviteEmailsToTeamAndChannels(
 			mlog.Error("Failed to send invite email successfully ", mlog.Err(err))
 		}
 
-		if nErr := es.SendMailWithEmbeddedFiles(invite, subject, body, embeddedFiles, "", "", ""); nErr != nil {
+		if nErr := es.SendMailWithEmbeddedFiles(invite, subject, body, embeddedFiles, "", "", "", "InviteEmailToTeamsAndChannels"); nErr != nil {
 			mlog.Error("Failed to send invite email successfully", mlog.Err(nErr))
 			if errorWhenNotSent {
 				inviteWithError := &model.EmailInviteWithError{
@@ -828,7 +837,7 @@ func (es *Service) SendDeactivateAccountEmail(email string, locale, siteURL stri
 		return err
 	}
 
-	if err := es.sendMail(email, subject, body); err != nil { // this needs to receive the header options
+	if err := es.sendMail(email, subject, body, "DeactivateAccountEmail"); err != nil { // this needs to receive the header options
 		return err
 	}
 
@@ -839,39 +848,47 @@ func (es *Service) SendNotificationMail(to, subject, htmlBody string) error {
 	if !*es.config().EmailSettings.SendEmailNotifications {
 		return nil
 	}
-	return es.sendMail(to, subject, htmlBody)
+	return es.sendMail(to, subject, htmlBody, "NotificationEmail")
 }
 
-func (es *Service) sendMail(to, subject, htmlBody string) error {
+func (es *Service) sendMail(to, subject, htmlBody, category string) error {
-	return es.sendMailWithCC(to, subject, htmlBody, "")
+	return es.sendMailWithCC(to, subject, htmlBody, "", category)
 }
 
-func (es *Service) sendEmailWithCustomReplyTo(to, subject, htmlBody, replyToAddress string) error {
+func (es *Service) sendEmailWithCustomReplyTo(to, subject, htmlBody, replyToAddress, category string) error {
 	license := es.license()
 	mailConfig := es.mailServiceConfig(replyToAddress)
 
-	return mail.SendMailUsingConfig(to, subject, htmlBody, mailConfig, license != nil && *license.Features.Compliance, "", "", "", "")
+	category = getSendGridCategory(category, license.IsCloud())
+
+	return mail.SendMailUsingConfig(to, subject, htmlBody, mailConfig, license != nil && *license.Features.Compliance, "", "", "", "", category)
 }
 
-func (es *Service) sendMailWithCC(to, subject, htmlBody string, ccMail string) error {
+func (es *Service) sendMailWithCC(to, subject, htmlBody, ccMail, category string) error {
 	license := es.license()
 	mailConfig := es.mailServiceConfig("")
 
-	return mail.SendMailUsingConfig(to, subject, htmlBody, mailConfig, license != nil && *license.Features.Compliance, "", "", "", ccMail)
+	category = getSendGridCategory(category, license.IsCloud())
+
+	return mail.SendMailUsingConfig(to, subject, htmlBody, mailConfig, license != nil && *license.Features.Compliance, "", "", "", ccMail, category)
 }
 
-func (es *Service) SendMailWithEmbeddedFilesAndCustomReplyTo(to, subject, htmlBody, replyToAddress string, embeddedFiles map[string]io.Reader) error {
+func (es *Service) SendMailWithEmbeddedFilesAndCustomReplyTo(to, subject, htmlBody, replyToAddress string, embeddedFiles map[string]io.Reader, category string) error {
 	license := es.license()
 	mailConfig := es.mailServiceConfig(replyToAddress)
 
-	return mail.SendMailWithEmbeddedFilesUsingConfig(to, subject, htmlBody, embeddedFiles, mailConfig, license != nil && *license.Features.Compliance, "", "", "", "")
+	category = getSendGridCategory(category, license.IsCloud())
+
+	return mail.SendMailWithEmbeddedFilesUsingConfig(to, subject, htmlBody, embeddedFiles, mailConfig, license != nil && *license.Features.Compliance, "", "", "", "", category)
 }
 
-func (es *Service) SendMailWithEmbeddedFiles(to, subject, htmlBody string, embeddedFiles map[string]io.Reader, messageID string, inReplyTo string, references string) error {
+func (es *Service) SendMailWithEmbeddedFiles(to, subject, htmlBody string, embeddedFiles map[string]io.Reader, messageID string, inReplyTo string, references string, category string) error {
 	license := es.license()
 	mailConfig := es.mailServiceConfig("")
 
-	return mail.SendMailWithEmbeddedFilesUsingConfig(to, subject, htmlBody, embeddedFiles, mailConfig, license != nil && *license.Features.Compliance, messageID, inReplyTo, references, "")
+	category = getSendGridCategory(category, license.IsCloud())
+
+	return mail.SendMailWithEmbeddedFilesUsingConfig(to, subject, htmlBody, embeddedFiles, mailConfig, license != nil && *license.Features.Compliance, messageID, inReplyTo, references, "", category)
 }
 
 func (es *Service) InvalidateVerifyEmailTokensForUser(userID string) *model.AppError {
@@ -965,7 +982,7 @@ func (es *Service) SendLicenseInactivityEmail(email, name, locale, siteURL strin
 		return err
 	}
 
-	if err := es.sendMail(email, subject, body); err != nil {
+	if err := es.sendMail(email, subject, body, "LicenseInactivityEmail"); err != nil {
 		return err
 	}
 
@@ -993,7 +1010,7 @@ func (es *Service) SendLicenseUpForRenewalEmail(email, name, locale, siteURL, re
 		return err
 	}
 
-	if err := es.sendMail(email, subject, body); err != nil {
+	if err := es.sendMail(email, subject, body, "LicenseUpForRenewal"); err != nil {
 		return err
 	}
 
@@ -1026,7 +1043,7 @@ func (es *Service) SendPaymentFailedEmail(email string, locale string, failedPay
 		return false, err
 	}
 
-	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail); err != nil {
+	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail, "PaymentFailed"); err != nil {
 		return false, err
 	}
 
@@ -1053,7 +1070,7 @@ func (es *Service) SendNoCardPaymentFailedEmail(email string, locale string, sit
 		return err
 	}
 
-	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail); err != nil {
+	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail, "NoCardPaymentFailed"); err != nil {
 		return err
 	}
 
@@ -1083,7 +1100,7 @@ func (es *Service) SendDelinquencyEmail7(email, locale, siteURL, planName string
 		return err
 	}
 
-	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail); err != nil {
+	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail, "Delinquency7"); err != nil {
 		return err
 	}
 
@@ -1112,7 +1129,7 @@ func (es *Service) SendDelinquencyEmail14(email, locale, siteURL, planName strin
 		return err
 	}
 
-	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail); err != nil {
+	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail, "Delinquency14"); err != nil {
 		return err
 	}
 
@@ -1142,7 +1159,7 @@ func (es *Service) SendDelinquencyEmail30(email, locale, siteURL, planName strin
 		return err
 	}
 
-	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail); err != nil {
+	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail, "Delinquency30"); err != nil {
 		return err
 	}
 
@@ -1174,7 +1191,7 @@ func (es *Service) SendDelinquencyEmail45(email, locale, siteURL, planName, deli
 		return err
 	}
 
-	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail); err != nil {
+	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail, "Delinquency45"); err != nil {
 		return err
 	}
 
@@ -1207,7 +1224,7 @@ func (es *Service) SendDelinquencyEmail60(email, locale, siteURL string) error {
 		return err
 	}
 
-	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail); err != nil {
+	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail, "Delinquency60"); err != nil {
 		return err
 	}
 
@@ -1240,7 +1257,7 @@ func (es *Service) SendDelinquencyEmail75(email, locale, siteURL, planName, deli
 		return err
 	}
 
-	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail); err != nil {
+	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail, "Delinquency75"); err != nil {
 		return err
 	}
 
@@ -1272,7 +1289,7 @@ func (es *Service) SendDelinquencyEmail90(email, locale, siteURL string) error {
 		return err
 	}
 
-	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail); err != nil {
+	if err := es.sendEmailWithCustomReplyTo(email, subject, body, *es.config().SupportSettings.SupportEmail, "Delinquency90"); err != nil {
 		return err
 	}
 
@@ -1297,7 +1314,7 @@ func (es *Service) SendRemoveExpiredLicenseEmail(renewalLink, email string, loca
 		return err
 	}
 
-	if err := es.sendMail(email, subject, body); err != nil {
+	if err := es.sendMail(email, subject, body, "RemoveExpiredLicense"); err != nil {
 		return err
 	}
 

app/email/email_batching.go

@@ -346,7 +346,7 @@ func (es *Service) sendBatchedEmailNotification(userID string, notifications []*
 		mlog.Error("Unable to render email", mlog.Err(renderErr))
 	}
 
-	if nErr := es.SendMailWithEmbeddedFiles(user.Email, subject, renderedPage, embeddedFiles, "", "", ""); nErr != nil {
+	if nErr := es.SendMailWithEmbeddedFiles(user.Email, subject, renderedPage, embeddedFiles, "", "", "", "BatchedEmailNotification"); nErr != nil {
 		mlog.Warn("Unable to send batched email notification", mlog.String("email", user.Email), mlog.Err(nErr))
 	}
 }

app/email/mocks/ServiceInterface.go

@@ -372,13 +372,13 @@ func (_m *ServiceInterface) SendLicenseUpForRenewalEmail(_a0 string, name string
 	return r0
 }
 
-// SendMailWithEmbeddedFiles provides a mock function with given fields: to, subject, htmlBody, embeddedFiles, messageID, inReplyTo, references
+// SendMailWithEmbeddedFiles provides a mock function with given fields: to, subject, htmlBody, embeddedFiles, messageID, inReplyTo, references, category
-func (_m *ServiceInterface) SendMailWithEmbeddedFiles(to string, subject string, htmlBody string, embeddedFiles map[string]io.Reader, messageID string, inReplyTo string, references string) error {
+func (_m *ServiceInterface) SendMailWithEmbeddedFiles(to string, subject string, htmlBody string, embeddedFiles map[string]io.Reader, messageID string, inReplyTo string, references string, category string) error {
-	ret := _m.Called(to, subject, htmlBody, embeddedFiles, messageID, inReplyTo, references)
+	ret := _m.Called(to, subject, htmlBody, embeddedFiles, messageID, inReplyTo, references, category)
 
 	var r0 error
-	if rf, ok := ret.Get(0).(func(string, string, string, map[string]io.Reader, string, string, string) error); ok {
+	if rf, ok := ret.Get(0).(func(string, string, string, map[string]io.Reader, string, string, string, string) error); ok {
-		r0 = rf(to, subject, htmlBody, embeddedFiles, messageID, inReplyTo, references)
+		r0 = rf(to, subject, htmlBody, embeddedFiles, messageID, inReplyTo, references, category)
 	} else {
 		r0 = ret.Error(0)
 	}

app/email/service.go

@@ -140,7 +140,7 @@ type ServiceInterface interface {
 	SendInviteEmailsToTeamAndChannels(team *model.Team, channels []*model.Channel, senderName string, senderUserId string, senderProfileImage []byte, invites []string, siteURL string, reminderData *model.TeamInviteReminderData, message string, errorWhenNotSent bool, isSystemAdmin bool, isFirstAdmin bool) ([]*model.EmailInviteWithError, error)
 	SendDeactivateAccountEmail(email string, locale, siteURL string) error
 	SendNotificationMail(to, subject, htmlBody string) error
-	SendMailWithEmbeddedFiles(to, subject, htmlBody string, embeddedFiles map[string]io.Reader, messageID string, inReplyTo string, references string) error
+	SendMailWithEmbeddedFiles(to, subject, htmlBody string, embeddedFiles map[string]io.Reader, messageID string, inReplyTo string, references string, category string) error
 	SendLicenseUpForRenewalEmail(email, name, locale, siteURL, renewalLink string, daysToExpiration int) error
 	SendPaymentFailedEmail(email string, locale string, failedPayment *model.FailedPayment, planName, siteURL string) (bool, error)
 	// Cloud delinquency email sequence

app/notification_email.go

@@ -130,7 +130,7 @@ func (a *App) sendNotificationEmail(c request.CTX, notification *PostNotificatio
 	}
 
 	a.Srv().Go(func() {
-		if nErr := a.Srv().EmailService.SendMailWithEmbeddedFiles(user.Email, html.UnescapeString(subjectText), bodyText, embeddedFiles, messageID, inReplyTo, references); nErr != nil {
+		if nErr := a.Srv().EmailService.SendMailWithEmbeddedFiles(user.Email, html.UnescapeString(subjectText), bodyText, embeddedFiles, messageID, inReplyTo, references, "Notification"); nErr != nil {
 			mlog.Error("Error while sending the email", mlog.String("user_email", user.Email), mlog.Err(nErr))
 		}
 	})

app/security_update_check.go

@@ -121,7 +121,7 @@ func (s *Server) DoSecurityUpdateCheck() {
 						mlog.Info("Sending security bulletin", mlog.String("bulletin_id", bulletin.Id), mlog.String("user_email", user.Email))
 						license := s.License()
 						mailConfig := s.MailServiceConfig()
-						mail.SendMailUsingConfig(user.Email, i18n.T("mattermost.bulletin.subject"), string(body), mailConfig, license != nil && *license.Features.Compliance, "", "", "", "")
+						mail.SendMailUsingConfig(user.Email, i18n.T("mattermost.bulletin.subject"), string(body), mailConfig, license != nil && *license.Features.Compliance, "", "", "", "", "SecurityUpdateCheck")
 					}
 
 					bulletinSeen := &model.System{Name: "SecurityBulletin_" + bulletin.Id, Value: bulletin.Id}

shared/mail/mail.go

@@ -57,6 +57,7 @@ type mailData struct {
 	messageID     string
 	inReplyTo     string
 	references    string
+	category      string
 }
 
 // smtpClient is implemented by an smtp.Client. See https://golang.org/pkg/net/smtp/#Client.
@@ -234,7 +235,7 @@ func TestConnection(config *SMTPConfig) error {
 	return nil
 }
 
-func SendMailWithEmbeddedFilesUsingConfig(to, subject, htmlBody string, embeddedFiles map[string]io.Reader, config *SMTPConfig, enableComplianceFeatures bool, messageID string, inReplyTo string, references string, ccMail string) error {
+func SendMailWithEmbeddedFilesUsingConfig(to, subject, htmlBody string, embeddedFiles map[string]io.Reader, config *SMTPConfig, enableComplianceFeatures bool, messageID string, inReplyTo string, references string, ccMail string, category string) error {
 	fromMail := mail.Address{Name: config.FeedbackName, Address: config.FeedbackEmail}
 	replyTo := mail.Address{Name: config.FeedbackName, Address: config.ReplyToAddress}
 
@@ -250,13 +251,14 @@ func SendMailWithEmbeddedFilesUsingConfig(to, subject, htmlBody string, embedded
 		messageID:     messageID,
 		inReplyTo:     inReplyTo,
 		references:    references,
+		category:      category,
 	}
 
 	return sendMailUsingConfigAdvanced(mail, config)
 }
 
-func SendMailUsingConfig(to, subject, htmlBody string, config *SMTPConfig, enableComplianceFeatures bool, messageID string, inReplyTo string, references string, ccMail string) error {
+func SendMailUsingConfig(to, subject, htmlBody string, config *SMTPConfig, enableComplianceFeatures bool, messageID string, inReplyTo string, references string, ccMail, category string) error {
-	return SendMailWithEmbeddedFilesUsingConfig(to, subject, htmlBody, nil, config, enableComplianceFeatures, messageID, inReplyTo, references, ccMail)
+	return SendMailWithEmbeddedFilesUsingConfig(to, subject, htmlBody, nil, config, enableComplianceFeatures, messageID, inReplyTo, references, ccMail, category)
 }
 
 // allows for sending an email with differing MIME/SMTP recipients
@@ -287,6 +289,8 @@ func sendMailUsingConfigAdvanced(mail mailData, config *SMTPConfig) error {
 	return sendMail(c, mail, time.Now(), config)
 }
 
+const SendGridXSMTPAPIHeader = "X-SMTPAPI"
+
 func sendMail(c smtpClient, mail mailData, date time.Time, config *SMTPConfig) error {
 	mlog.Debug("sending mail", mlog.String("to", mail.smtpTo), mlog.String("subject", mail.subject))
 
@@ -307,6 +311,11 @@ func sendMail(c smtpClient, mail mailData, date time.Time, config *SMTPConfig) e
 		"Precedence":                {"bulk"},
 	}
 
+	if mail.category != "" {
+		sendgridHeader := fmt.Sprintf(`{"category": %q}`, mail.category)
+		headers[SendGridXSMTPAPIHeader] = []string{sendgridHeader}
+	}
+
 	if mail.replyTo.Address != "" {
 		headers["Reply-To"] = []string{mail.replyTo.String()}
 	}

shared/mail/mail_test.go

@@ -124,7 +124,7 @@ func TestSendMailUsingConfig(t *testing.T) {
 	//Delete all the messages before check the sample email
 	DeleteMailBox(emailTo)
 
-	err2 := SendMailUsingConfig(emailTo, emailSubject, emailBody, cfg, true, "", "", "", emailCC)
+	err2 := SendMailUsingConfig(emailTo, emailSubject, emailBody, cfg, true, "", "", "", emailCC, "")
 	require.NoError(t, err2, "Should connect to the SMTP Server")
 
 	//Check if the email was send to the right email address
@@ -162,7 +162,7 @@ func TestSendMailWithEmbeddedFilesUsingConfig(t *testing.T) {
 		"test1.png": bytes.NewReader([]byte("xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx")),
 		"test2.png": bytes.NewReader([]byte("xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx")),
 	}
-	err2 := SendMailWithEmbeddedFilesUsingConfig(emailTo, emailSubject, emailBody, embeddedFiles, cfg, true, "", "", "", emailCC)
+	err2 := SendMailWithEmbeddedFilesUsingConfig(emailTo, emailSubject, emailBody, embeddedFiles, cfg, true, "", "", "", emailCC, "")
 	require.NoError(t, err2, "Should connect to the SMTP Server")
 
 	//Check if the email was send to the right email address
@@ -407,7 +407,7 @@ func TestSendMail(t *testing.T) {
 
 	for testName, tc := range testCases {
 		t.Run(testName, func(t *testing.T) {
-			mail := mailData{"", "", mail.Address{}, "", tc.replyTo, "", "", nil, nil, tc.messageID, tc.inReplyTo, tc.references}
+			mail := mailData{"", "", mail.Address{}, "", tc.replyTo, "", "", nil, nil, tc.messageID, tc.inReplyTo, tc.references, ""}
 			cfg := getConfig()
 			err = sendMail(mocm, mail, time.Now(), cfg)
 			require.NoError(t, err)