One year after i wrote this : http://felix.sportelli.org/blog/index.php/2005/11/11/85-postfixsaslmd5 i just had the same problem. Thanks for me i wrote down this post :) But the problem was still there, why did i have this error : warning: SASL authentication failure: cannot connect to saslauthd server: Permission denied.

Ok, i had to rembember myself that postfix was not in the sasl group ... a simple adduser postfix sasl and here it is !

Just, if you want to test your authenticated mail server, this is how to do it : 

neo@enigma:~$ printf 'me@mydomain.com\0me@mydomain.tld\0mypass' | mimencode
bWVAbXlkb21haW4uprout9tYWluLnRsZABteXBhc3M=

neo@enigma:~$ telnet mail.mydomain.com 25
Trying xxx.xxx.xxx.xxx ...
Connected to mail.mydomain.com.
Escape character is '^]'.
220 mymailserv.mydomain.com ESMTP Postfix (Debian/GNU)
ehlo enigma.ordrejedis.net
250-mymailserv.mydomain.com
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-AUTH LOGIN PLAIN
250-AUTH=LOGIN PLAIN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
auth plain bmVvQHltZW11c2ljLmNvbQBuZW9AeW1lbXVzaWMuY29tAHRlc3Q=
235 2.0.0 Authentication successful
mail from:
250 2.1.0 Ok
rcpt to:
250 2.1.5 Ok
DATA
354 End data with .

it worksssssss !!!

.
250 2.0.0 Ok: queued as 3E366BC263
And this is it !