Can’t connect to TLS via IMAP – Exchange 2010
error messages on secure IMAP clients, and forcing client access imap4 to tls on port 143 won’t allow you to connect unsecurely.
TLS must have a certificate enabled on IMAP.
Must be done in the Exchange Management Shell:
this will give you the thumprints of existing certificates in exchange. If you don’t have one with an I in “Services” you will need to enable one.
Enable-ExchangeCertificate -Thumbprint 66yourthumbprint5532E1450907958EC9D2F1E1A3 -Services IMAP
This will enable the certificate on IMAP4/tls. If you do not enable a certificate, you cannot connect with tls (and likely SSL)
Microsoft Exchange IMAP4
If you have credential errors after the fact, try DOMAINusername