When a client’s site connects to the server, the server can offer authentication by presenting the AUTH keyword, followed by authentication mechanisms supported:
250-host.domain Hello some.domain, pleased to meet you 250-ENHANCEDSTATUSCODES 250-PIPELINING 250-8BITMIME 250-SIZE 250-DSN 250-ETRN 250-AUTH DIGEST-MD5 CRAM-MD5 KERBEROS-V4 ←note this line 250-DELIVERBY 250 HELP
If the connecting site wishes to authenticate itself, it replies with an AUTH command indicating the desired mechanism:
AUTH CRAM-MD5 ← authentication challenge here ← authentication reply here 235 Authentication successful.← server replies
This interaction automatically establishes an authenticated stream using the CRAM-MD5 method.
If you wish to turn off additional encryption in SASL when STARTTLS
is already encrypting the communication, you do so by defining this
AuthMaxBits option. When set, this option limits
the maximum encryption strength for the security layer in SMTP AUTH.
When not set (the default) encryption strength is essentially
AuthMaxBits option is used like
O AuthMaxBits=limit ← configuration file (V8.12 and later) -OAuthMaxBits=limit ← command line (V8.12 and later) define(`confAUTH_MAX_BITS', `limit')← mc configuration (V8.12 and later)
Here, limit is the maximum number of bits in the keylength. The existing encryption strength is taken into account when choosing an algorithm for the security layer. For example, if STARTTLS is used and the symmetric ...