Azure Communication Services
An Azure communication platform for deploying applications across devices and platforms.
Only Creator is Allowed to Send SMTP of App
Kruize Christensen
0
Reputation points
I am creating an app for Amasty in Magento to send SMTP emails. We have a noreply email set up with SMTP enabled and it has been given Cloud Application Administrator. I had another admin try it that had more privilages then myself and they got the same error as the noreply email. My email can send these with no problem.
Azure Communication Services
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Golla Venkata Pavani 7,440 Reputation points Microsoft External Staff Moderator2026-04-22T21:57:54.8566667+00:00 Thank you for reaching us regarding the issue that your when sending emails via SMTP using an application (App Registration), email sending is controlled by application permissions and mailbox-level authorization, not by user roles such as Global Admin or Cloud Application Administrator.
SMTP authentication with modern authentication uses a Microsoft Entra application (service principal) to send emails.To send email successfully, the application must be granted the appropriate permissions, such as SMTP.SendAsApp (Exchange Online) or Mail.Send (Microsoft Graph), and these permissions must have admin consent at the tenant level. Additionally, the application must be explicitly authorized in Exchange Online to send email on behalf of (or as) a specific mailbox.
If the application is not properly authorized for the target mailbox, Exchange Online restricts email sending. This can result in errors such as“Only Creator is Allowed to Send SMTP of App”, where sending is effectively limited to the configured or authorized identity.
Required Configuration:
- Application permissions
- The app must have either SMTP.SendAsApp (Exchange Online) or Mail.Send (Microsoft Graph) permission, and admin consent must be granted for the app to send emails successfully.
- Mailbox authorization
- The application (service principal) must have permission to send as the noreply mailbox
- SMTP sending requires explicit mailbox-level authorization.
- Access scope (if configured)
- If application access policies or RBAC are used, confirm the noreply mailbox is included
- Applications can be restricted to specific mailboxes only.
- SMTP AUTH enabled
- SMTP AUTH must be enabled for the mailbox or tenant
Kindly let us know if the above helps or you need further assistance on this issue.
Please "upvote" if the information helped you. This will help us and others in the community as well.
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Kruize Christensen 0 Reputation points
2026-04-23T14:32:53.3233333+00:00 I went through those and i am still getting an error.
I keep getting the error "Error: 2.54258:00000000, 0.59634:22000000, 1.56562:00000000, 1.55954:0A000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:12000000, 1.56562:00000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:2C000000, 1.56562:00000000, 1.55954:0A000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:22000000, 1.56562:00000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:22000000, 1.56562:00000000, 1.64146:0E000000, 1.33010:0E000000, 2.54258:00000000, 1.33010:0E000000, 2.54258:00000000, 1.64146:32000000, 1.33010:32000000, 2.54258:DC040000, 1.33010:32000000, 2.54258:DC040000, 255.79500:00000000, 0.100684:00000000, 255.66700:00000000, 5.95292:67000000446F526F7073006E, 8.111356:9552F9FE86593ECC1F1F572B2F8F6BAC0BAFA94C, 0.38698:B2223003, 1.41134:86000000, 1.41134:86000000, 1.41134:86000000, 1.41134:46000000, 0.37692:00000000, 0.44092:00000000, 0.84132:9552F9FE, 0.41232:1F1F572B, 0.60208:A6536B31, 0.37136:86000000, 0.34608:655FD59D, 0.55056:86000000, 0.42768:01000000, 0.56112:1C000000, 0.52807:0A000000, 0.46663:0000000"
Here is the guide I am using to set this up.
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Golla Venkata Pavani 7,440 Reputation points Microsoft External Staff Moderator
2026-04-23T22:20:24.2233333+00:00 Thank you for the update and for sharing the configuration you followed.
The issue is caused by a misalignment between Magento (Amasty SMTP) configuration and Microsoft 365 SMTP (OAuth) requirements.
- The Amasty extension only configures the SMTP client on the Magento side
- However, Microsoft 365 requires additional backend configuration (App registration, permissions, and mailbox authorization) for SMTP with OAuth.
- SMTP with OAuth requires a Microsoft Entra application with appropriate permissions and admin consent
- The application must also be explicitly authorized to send email from the target mailbox
- Without this authorization, email sending will fail even if admin roles are assigned.
The error persists because authentication may succeed, but authorization or SMTP OAuth configuration is incomplete. This usually happens when the app lacks proper mailbox access or required permissions.
Recommendations:
Please review the following required configuration areas:- Authentication Method in Magento (Amasty)
- Must use OAuth 2.0 (Microsoft)
- Login/Password authentication is deprecated for Microsoft and will not work reliably
- Microsoft Entra App Configuration
- App must have:
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Mail.SendorSMTP.SendAsApppermission - Admin consent must be granted
- Mailbox Authorization (Critical)
- The application (service principal) must be explicitly allowed to send as the noreply mailbox
- Without this, SMTP sending will fail by design
- SMTP Settings
- Server:
smtp.office365.com - Port:
587 - Encryption:
STARTTLS/TLS
- Server:
If you can share whether you are using OAuth Client ID configuration in Amasty or still using username/password, I can help you pinpoint the exact missing configuration.
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Kruize Christensen 0 Reputation points
2026-04-24T13:25:22.3233333+00:00 I added SMTP.SendAsApp and Mail.Send. I am still getting the same error.
Also I am using OAUTH2 Client ID (Microsoft)
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Golla Venkata Pavani 7,440 Reputation points Microsoft External Staff Moderator
2026-04-24T17:11:04.53+00:00 Thanks for the update. You are using OAuth2 Client ID (Microsoft) and added
SMTP.SendAsAppandMail.Sendpermission.Granting SMTP.SendAsApp or Mail.Send permissions alone is not sufficient. The application must also be explicitly authorized to send as a specific mailbox in Exchange Online. This requirement is enforced either through an Exchange service principal with mailbox permissions or by using application access policies or RBAC scoping. It clearly states that application permissions do not automatically allow sending email from all mailboxes, so the app must be granted access to the intended target mailbox.
Recommended Fix:
You must explicitly grant the application permission to send as the mailbox.Step 1: Register the service principal in Exchange Online
New-ServicePrincipal -AppId <APP_ID> -ObjectId <ENTERPRISE_APP_OBJECT_ID>Step 2: Grant mailbox permissions
Add-MailboxPermission -Identity ******@yourdomain.com -User <ServicePrincipal> -AccessRights FullAccess Add-RecipientPermission -Identity ******@yourdomain.com -Trustee <ServicePrincipal> -AccessRights SendAsThis step is mandatory for SMTP.SendAsApp scenarios and is clearly required.
Reference:
https://docs.secureauth.com/2307/en/configure-smtp-with-oauth2-for-microsoft-365.html
https://learn.microsoft.com/en-us/exchange/client-developer/legacy-protocols/smtp-app-rbac-onboardingKindly let us know if the above helps or you need further assistance on this issue.
Please "upvote" if the information helped you. This will help us and others in the community as well.
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Kruize Christensen 0 Reputation points
2026-04-24T18:09:22.06+00:00 I completed step 1 and both of step 2 but I am still getting the same error.
Please, check module/application settings. Error: 2.54258:00000000, 0.59634:33000000, 1.56562:00000000, 1.55954:0A000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:0C000000, 1.56562:00000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:00000000, 1.56562:00000000, 1.55954:0A000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:00000000, 1.56562:00000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:07000000, 1.56562:00000000, 1.64146:0E000000, 1.33010:0E000000, 2.54258:00000000, 1.33010:0E000000, 2.54258:00000000, 1.64146:32000000, 1.33010:32000000, 2.54258:DC040000, 1.33010:32000000, 2.54258:DC040000, 255.79500:00000000, 0.100684:00000000, 255.66700:00000000, 5.95292:67000000446F526F70730054, 8.111356:9552F9FE86593ECC1F1F572B2F8F6BACA6536B31, 0.38698:A6536B31, 1.41134:86000000, 1.41134:86000000, 1.41134:86000000, 1.41134:46000000, 0.37692:140F76A6, 0.44092:86000000, 0.84132:2C000000, 0.41232:00000000, 0.60208:46000000, 0.37136:46000000, 0.34608:01000000, 0.55056:B9B80A03, 0.42768:0A000000, 0.56112:00000000, 0.52807:0F010480, 0.46663:8600000
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Golla Venkata Pavani 7,440 Reputation points Microsoft External Staff Moderator
2026-04-25T00:12:42.4366667+00:00 Sorry to hear that issue isn't not resolved.
The behavior for SMTP with OAuth (Exchange Online), the error“Only Creator is Allowed to Send SMTP of App” indicates that the request is still being blocked at the mailbox authorization (access scope) level, even though authentication and permissions are configured.Applications must be granted access to mailboxes through RBAC for Applications or equivalent scoping mechanisms, otherwise access is denied.
The most likely causes are that the authorization scope is still not correctly applied, and the mailbox (noreply) may not be included in the effective access scope for the application; additionally, there may be a mixed configuration model, combining RBAC with mailbox-level permissions (such as SendAs and FullAccess), which can lead to conflicts causing Exchange to reject the request; finally, SMTP AUTH may not be fully enabled, and it must be enabled at the mailbox or tenant level for SMTP submission to work.
Recommendations:
Option 1 : RBAC for Applications- Ensure Service Principal is created and define a scope that includes the noreply mailbox
- Assign role:
New-ManagementRoleAssignment -Name "SMTPAppAccess" -Role "Application SMTP.SendAsApp" -App <AppId> -CustomResourceScope "<ScopeName>"
Ensure:
- The mailbox is included in the scope
- Do not use
Add-MailboxPermissionorAdd-RecipientPermission
Option 2 (Legacy model – mailbox permission approach)
If you are not using RBAC, you should keep the configuration limited to New-ServicePrincipal, Add-MailboxPermission, and Add-RecipientPermission, while also ensuring that no RBAC role assignments exist to avoid conflicts or unintended access issues.
- Mandatory Validation Verify SMTP AUTH is enabled for the mailbox:
expected result: false, SMTP AUTH must be enabled for SMTP client submission to workGet-CASMailbox ******@domain.com | fl SmtpClientAuthenticationDisabled
Reference:
https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/authenticated-client-smtp-submission
https://learn.microsoft.com/en-us/exchange/client-developer/legacy-protocols/smtp-app-rbac-onboarding
Kindly let us know if the above helps or you need further assistance on this issue.Please "upvote" if the information helped you. This will help us and others in the community as well.
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Kruize Christensen 0 Reputation points
2026-04-27T13:59:28.9466667+00:00 I am still having the same issue after adding the first part, and the result from CASMailbox was false.
Please, check module/application settings. Error: 2.54258:00000000, 0.59634:00000000, 1.56562:00000000, 1.55954:0A000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:03000000, 1.56562:00000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:00000000, 1.56562:00000000, 1.55954:0A000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:00000000, 1.56562:00000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:07000000, 1.56562:00000000, 1.64146:0E000000, 1.33010:0E000000, 2.54258:00000000, 1.33010:0E000000, 2.54258:00000000, 1.64146:32000000, 1.33010:32000000, 2.54258:DC040000, 1.33010:32000000, 2.54258:DC040000, 255.79500:00000000, 0.100684:00000000, 255.66700:00000000, 5.95292:67000000446F526F7073006E, 8.111356:9552F9FE86593ECC1F1F572B2F8F6BAC0BAFA94C, 0.38698:A46078CF, 1.41134:86000000, 1.41134:86000000, 1.41134:86000000, 1.41134:46000000, 0.37692:00000000, 0.44092:140F76A6, 0.84132:86000000, 0.41232:00000000, 0.60208:00000000, 0.37136:FB790100, 0.34608:86000000, 0.55056:16000000, 0.42768:00000000, 0.56112:02000000, 0.52807:00653036, 0.46663:1600000
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Kruize Christensen 0 Reputation points
2026-04-28T15:47:49.3133333+00:00 I added Option 1 and I also verified option 2
Please, check module/application settings. Error: 1.56562:00000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:FE000000, 1.56562:00000000, 1.64146:0E000000, 1.33010:0E000000, 2.54258:00000000, 1.33010:0E000000, 2.54258:00000000, 1.64146:32000000, 1.33010:32000000, 2.54258:DC040000, 1.33010:32000000, 2.54258:DC040000, 255.79500:00000000, 0.100684:00000000, 255.66700:00000000, 5.95292:67000000446F526F7073006E, 8.111356:9552F9FE86593ECC1F1F572B2F8F6BACA6536B31, 0.38698:A6536B31, 1.41134:86000000, 1.41134:46000000, 0.37692:140F76A6, 0.44092:000F76A6, 0.41232:140F76A6, 0.60208:00000000, 0.37136:1E000000, 0.34608:9552F9FE, 0.55056:1F1F572B, 0.42768:EA8C0100, 0.56112:86000000, 0.52807:86000000, 0.46663:AB040000, 1.41134:46000000, 7.36354:010000000000010901000000, 1.46439:0A000000, 1.115228:00000000, 0.104668:2A000000, 1.44903:25000000, 1.115228:00000000, 0.57310:6E672E42, 0.38878:6E6E656C, 5.50564:00000000532D312D352D32312D323333383733323231362D3439373836393233362D3434383438343839382D353836383537363800A5DE0888000100, 5.33016:DC040000534F424F2072
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Kruize Christensen 0 Reputation points
2026-05-06T14:56:59.5766667+00:00 Redid the app and followed the steps, and got it to work.
Also modified the store email in Amasty when first signing in.
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