Office 365 Credentials Flow in MailBee.NET Objects v12.3.1

Wednesday, 23 November 2022

Dear MailBee.NET users,

As you may know, Office 365 will no longer support login/password authentication for IMAP/POP3 protocols. The clients must now use OAuth 2.0 instead.

The just released MailBee.NET Objects v12.3.1 now includes OAuth 2.0 for Office 365 Accounts (non-interactive mode) manual on how to set up Office 365 environment and get the access token using Microsoft Identity API and without the end user's interaction.

Previous versions of MailBee.NET Objects have already been shipped with OAuth 2.0 manuals for Office 365 but they provided only interactive flows where the end user must explicitly grant consent for your app to access their email. Now Office 365 gained support of Credentials Flow (Client Credentials Grant) which does not require the end user's participation, is simpler to use and works the same way for all kinds of applications.

Note that Office 365 supports Credentials Flow for IMAP/POP3 and EWS but not for SMTP. It's not known yet when SMTP support gets added there. Currently, SMTP operates as before, via login/password authentication.

Download page

Other changes in v12.3.1:

  • Improved conversion of signed/encrypted messages from EML to Outlook MSG.
  • Misc. TLS 1.2 and TLS 1.3 improvements.
  • SHA265RSA support in S/MIME.
  • Improved RTF-to-HTML conversion (Outlook MSG to EML).

This update is compatible with the existing v12 keys. Still, you need to have a valid maintenance contract in order to upgrade. In case if your maintenance contract has already expired, you'll need to renew it first. This can be done at (or just drop us a message if your key is not recognized).

Having questions? We're all ears at

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