This was fixed by changing the support version of the TLS protocol.
The default has changed to TLS version 3.
In Linux I go to:
- Scroll all the way to the bottom
- Config Editor button
- I accept the risk
- search for
- change default to what ever your server supports
I used the following to check what the server supported
openssl s_client -starttls imap -tls1 -connect exch1.email.somedomain.com:143 | grep 'New,'
New, TLSv1.0, Cipher is ECDHE-RSA-AES256-SHA
Unfortunately, there are not other supported versions
openssl s_client -starttls imap -tls1_3 -connect exch1.email.newsclip.co.za:143 | grep 'New,
New, (NONE), Cipher is (NONE)
Will need to send the admins a stern email telling them to patch and upgrade.
We will actually migrate to something that is not an MS product.
For more info checkout