Linux – How to configure postfix for per-sender SASL authentication

I have two gmail accounts, and I want to configure my local postfix server as a client which does SASL authentication with smtp.gmail.com:587 with credentials that depend on the sender address.

So, let's say that my gmail accounts are: acc1@gmail.com and acc2@gmail.com. If I sent a mail with acc1@gmail.com in the FROM header field, then postfix should use the credentials: acc1@gmail.com:psswd1 to do SASL authentication with gmail SMTP server. Similarly with acc2@gmail.com, it should use acc2@gmail.com:passwd2. Sounds fairly simple.

Well, I followed the postfix official documentation at http://www.postfix.org/SASL_README.html, and I ended up with the following relevant configurations:

/etc/postfix/main.cf

    smtp_sasl_auth_enable = yes
    smtp_sasl_security_options = noanonymous
    smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
    smtp_sender_dependent_authentication = yes
    sender_dependent_relayhost_maps = hash:/etc/postfix/sender_relay

    smtp_tls_security_level = secure
    smtp_tls_CAfile = /etc/ssl/certs/Equifax_Secure_CA.pem
    smtp_tls_CApath = /etc/ssl/certs
    smtp_tls_session_cache_database = btree:/etc/postfix/smtp_scache
    smtp_tls_session_cache_timeout = 3600s
    smtp_tls_loglevel = 1
    tls_random_source = dev:/dev/urandom

    relayhost = smtp.gmail.com:587

/etc/postfix/sasl_passwd

    acc1@gmail.com      acc1@gmail.com:passwd1
    acc2@gmail.com      acc2@gmail.com:passwd2

    smtp.gmail.com:587  acc1@gmail.com:passwd1

/etc/postfix/sender_relay

    acc1@gmail.com      smtp.gmail.com:587
    acc2@gmail.com      smtp.gmail.com:587

After I'm done with the configurations I did:

    $ postmap /etc/postfix/sasl_passwd
    $ postmap /etc/postfix/sender_relay
    $ /etc/init.d/postfix restart

The problem is that when I send a mail from acc2@gmail.com, the message ends up in the destination with sender address acc1@gmail.com and NOT acc2@gmail.com, which means that postfix always ignores the per-sender configurations and send the mail using the default credentials (the third line in /etc/postfix/sasl_passwd above). I checked the configurations multiple times and even compared them to those in various blog posts addressing the same issue but found them to be more or less the same as mine. So, can anyone point me in the right direction, in case I'm missing something?

Many thanks.

EDIT:

Here is what goes into /var/log/mail.log when I send a mail from acc2@gmail.com to another "obfuscated" mail address, acc3@isp.com

            Sep 11 17:28:24 host postfix/pickup[13235]: D0E71A4167D: uid=1000 from=<marwan>
    Sep 11 17:28:24 host postfix/cleanup[13259]: D0E71A4167D: message-id=<20120911152824.GX10881@host>
    Sep 11 17:28:24 host postfix/qmgr[13236]: D0E71A4167D: from=<marwan@host>, size=413, nrcpt=1 (queue active)
    Sep 11 17:28:25 host postfix/smtp[13263]: setting up TLS connection to smtp.gmail.com[173.194.70.108]:587
    Sep 11 17:28:25 host postfix/smtp[13263]: Verified TLS connection established to smtp.gmail.com[173.194.70.108]:587: TLSv1 with cipher RC4-SHA (128/128 bits)
    Sep 11 17:28:32 host postfix/smtp[13263]: D0E71A4167D: to=<acc3@isp.com>, relay=smtp.gmail.com[173.194.70.108]:587, delay=7.8, delays=0.1/0/2.7/5, dsn=2.0.0, status=sent (250 2.0.0 OK 1347377285 25sm9995878bkx.9)
    Sep 11 17:28:32 host postfix/qmgr[13236]: D0E71A4167D: removed

As for the MAIL FROM command I noticed it when I increased the tls logging level:

    Sep 11 18:26:53 host postfix/smtp[14287]: Write 42 chars: MAIL FROM:<marwan@host> SIZE=405 AUTH=<>

So, is the MAIL FROM command supposed to contain acc2@gmail.com? and if it is, what should I do to make it that way.

BTW, I didn't edit that last line; my local hostname is "host" and my local usename is "marwan".

Thanks again.