Office365 SMTP AUTH XOAUTH2 Fails with “535 5.7.3 Authentication unsuccessful”

If you successfully minted an OAuth2 access token for your Azure Entra Id App, but then it fails when attempting to use it in the SMTP protocol for sending email with the error: AUTH XOAUTH2 user=xxx auth=Bearer ********************** 535 5.7.3 Authentication unsuccessful [ 2024-04-16T12:11:26.548Z 08DC9999186DF999] Check your Entra Id App Registration to make sure you have the following App Permissions:

How to Troubleshoot Office365 IMAP AUTHENTICATE XOAUTH2 Failed

Question: We have an issue reading mail and we see the below error message in log Login: DllDate: Oct 27 2023 ChilkatVersion: UnlockPrefix: *** UnlockStatus: 2 Architecture: Little Endian; 32-bit Language: *** VerboseLogging: 0 imapServer: loginX(2219ms): login: greeting: * OK The Microsoft Exchange IMAP4 service is ready. [***] authenticateXOAuth2(2219ms): xoauth2Imap(2219ms): ConnectionType: SSL/TLS ImapCmdSent: aaab AUTHENTICATE XOAUTH2 ImapCmdResp: […]

Chilkat v9.5.0.98 Release Notes

Previous Version: Chilkat v9.5.0.98 Release Notes General: Removed all internal usage of the R250 random number generation algorithm and replaced with the more cryptographically secure Fortuna algorithm. DNS: Fixed various DNS problems having to do with VPNs or other uncommon situations. Ftp2: Fixed situation where CreateRemoteDir is called, but the remote directory already exists. In this case, CreateRemoteDir will […]