When a mail client connects to a mail server to receive or send mail, authentication is used for security purposes. There are different authentication methods. Some of the options are CRAM-MD5 or APOP, which are currently outdated and insecure. Here's how to check your current settings and set up a more modern and secure authentication method.
To properly configure authentication in the Mail app, do the following:
993
and check the box next to "Use TLS / SSL».143
and the unchecked box opposite “Use TLS / SSL».995
and check the box next to "Use TLS / SSL».110
and the unchecked box opposite “Use TLS / SSL».465
and check the box next to "Use TLS / SSL».25
or 2525
and the unchecked box opposite “Use TLS / SSL».