If your app/client does not support newer TLS versions, you have to use the "legacy" endpoint as detailed here: https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/opt-in-exchange-online-endpoint-for-legacy-tls-using-smtp-auth
Exchange Online Direct Send
Stellar 1990
20
Reputation points
Settings for direct send say TLS is optional. However, since depreciation of basic authentication, I am told by Microsoft 365 support staff this is no longer possible. Here's what the article currently says:
TLS/StartTLS Optional
Can you confirm Option 2 Direct send ( TLS/StartTLS Optional ) is possible
Exchange Online
Exchange Online
A Microsoft email and calendaring hosted service.
6,186 questions
Accepted answer
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Vasil Michev 119.7K Reputation points MVP Volunteer Moderator
2023-05-02T16:21:43.3666667+00:00