I use Outlook for Mac 2011 on a Macbook Pro with OS X Yosemite 10.10.5 

In early January my email provider upgraded its server from POP 3 to IMAP. Since then I've been unable to send or receive email in Outlook and receive the following error message: "Authentication failed because Outlook doesn't support any of the available authentication methods."

I contacted the email provider and initially they tried to help but when the problem continued they stopped replying. They are an activist-based outfit, not a commercial one.

I decided to try my partner's old Windows laptop and configured my email account on Outlook 2010. The port no.s are 993 for incoming (IMAP) and 587 for outgoing (SMTP). Encryption is SSL for IMAP and TLS for SMTP. Settings for outgoing server are the same as incoming. It worked! I was able to download my emails.

The only reason it appears I can't do that in Outlook for Mac 2011 is there's no option for TLS encryption on SMTP, just SSL. The only box to check is "Use SSL to connect (recommended)". Whether I tick that or leave it blank it doesn't work.

I would like any advice on what I can do. Can Outlook for Mac 2011 be configured for TLS encryption? Is there another version that will work this way? I don't want to change my email provider. Thanks.