Check Accepted Auth types
To check the currently available auth type you will need to use openssl
# openssl s_client -crlf -connect yourdomain.tld:465
...
...
#ehlo testing
250-yourdomain.tld
250-PIPELINING
250-SIZE 10240000
250-ETRN
250-AUTH DIGEST-MD5 CRAM-MD5 PLAIN LOGIN
250-ENHANCEDSTATUSCOD...0.0(0 votes)