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As Im sure you are aware, Microsoft is disabling access to their POP3 services via Basic Authentication.

I have been reading the article How to use OAuth2.0 authentication for Office365 with Rebex Secure Mail and EWS, IMAP, POP3 or SMTP and it references redirecting a user to a login page.

Our application is a background service so we dont have any user interaction.

Our version is quite old (purchased in 2018) and before we purchase the upgrade, I just wanted to check if we will be able to check POP3 emails with the Secure Mail client in the background without a signed in user?



Applies to: Rebex Secure Mail

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Yes, Microsoft will disable basic authentication in Office 365's POP3 and IMAP services on 2022-10-01. For SMTP, basic authentication will only be disabled for tenants where it's not being used.

Rebex Secure Mail does work with app-only (unattended) authentication, intended for background services and daemons. The old version might work as well, although the new one is better as it offers up-to-date TLS support and a new Login method overload that makes it easier to pass OAuth2.0 token to the server.

To get app-only authentication working with POP3 or IMAP, please follow our step-by-step guide:

For sending e-mails, either keep using SMTP with basic authentication for now (and hope that Microsoft eventually adds support for app-only mode to Office 365's SMTP as well), or switch to the EWS protocol, which supports message sending as well and is available in app-only mode.