We're reconfiguring osTicket now that OAuth is required for connecting to Microsoft 365. However, we seem to have lost the ability to use one account to authenticate to Send As a different account.

To detail our setup: We have one e-mail address "group@company.com" and one e-mail address "user@company.com."

user@company.com is a regular user mailbox, which osTicket uses to fetch e-mails to generate tickets. group@company.com is a distribution list / group, not an actual mailbox. user@company.com has "Send As" permissions granted in Delegate Access settings for group@company.com. So, user@company.com can be used to authenticate for sending messages as the group@company.com address.

This all worked perfectly fine with basic authentication. But now that we are using OAuth, osTicket gives this error when configuring the Outgoing (SMTP) settings:

Email Mismatch: Expecting Authorization for group@company.com not user@company.com

Is this an error on osTicket's side, if it is not designed to allow this type of set up? Or, am I missing some configuration in Microsoft 365 in the OAuth2 configuration?

(Sending and receiving as user@company.com is currently working fine.)

These are the API Permissions currently configured. Mail.Send.Shared should be the main one needed for the purpose at hand:

IMAP.AccessAsUser.All
Mail.ReadWrite
Mail.ReadWrite.Shared
Mail.Send
Mail.Send.Shared
offline_access
openid
POP.AccessAsUser.All
SMTP.Send
User.Read

Thanks for anyone's assistance! I know everyone is working through all these OAuth2 problems at the same time. 😅