virtual_alias_maps = pcre:/etc/postfix/forward_user.pcre, ...

/^(.*)@adomain.example/    $(1)@other-domain.example

virtual_alias_maps = regexp:/etc/postfix/virtual

/^([^@]*)@olddomain/ $(1)@newdomain

| source       | destination   |
|==============|===============|
| @example.com | @yoursite.com |

virtual_alias_domains = alias-destination1.com alias-destination2.com
virtual_alias_maps = hash:/etc/postfix/virtual

# I want @true-destination.com to have two incoming aliases
@alias-destination1.com @true-destination.com
@alias-destination2.com @true-destination.com

# telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 smtp.myserver.com ESMTP Postfix
HELO smtp.myserver.com
250 smtp.myserver.com
MAIL FROM:<somebody@gmail.com>
RCPT TO:<anyuser@alias-destination1.com>
250 2.1.5 Ok
DATA
354 End data with <CR><LF>.<CR><LF>
Message-ID: <4DC3723F.8010907@myserver.com>
Date: Thu, 05 May 2011 23:59:59 -0400
From: Some Body <somebody@gmail.com>
To: anyuser@alias-destination1.com
Subject: Hello
Just testing.
.

Apr  6 22:39:43 smtp-a postfix/smtpd[4411]: connect from localhost[127.0.0.1]
Apr  6 22:39:43 smtp-a postfix/smtpd[4411]: 6B47641AF2: client=localhost[127.0.0.1]
Apr  6 22:39:43 smtp-a postfix/cleanup[3706]: 6B47641AF2: message-id=<4DC3723F.8010907@myserver.com>
Apr  6 22:39:43 smtp-a postfix/qmgr[3681]: 6B47641AF2: from=<somebody@gmail.com>, size=1115, nrcpt=1 (queue active)
Apr  6 22:39:43 smtp-a postfix/smtpd[4411]: disconnect from localhost[127.0.0.1]
Apr  6 22:39:43 smtp-a amavis-incoming[2159]: (02159-13) Passed CLEAN {RelayedInternal}, LOCAL [127.0.0.1]:42426 [127.0.0.1] <somebody@gmail.com> -> <anyuser@alias-destination1.com>, Queue-ID: 5C61F41AE5, Message-ID: <4DC3723F.8010907@myserver.com>, mail_id: hUbzH1PtXlzl, Hits: 2.605, size: 394, queued_as: 6B47641AF2, 1224 ms
Apr  6 22:39:43 smtp-a postfix/lmtp[3687]: 5C61F41AE5: to=<anyuser@alias-destination1.com>, relay=127.0.0.1[127.0.0.1]:10024, delay=25, delays=24/0/0/1.2, dsn=2.0.0, status=sent (250 2.0.0 from MTA(smtp:[127.0.0.1]:10025): 250 2.0.0 Ok: queued as 6B47641AF2)
Apr  6 22:39:43 smtp-a postfix/qmgr[3681]: 5C61F41AE5: removed

Apr  6 22:39:43 smtp-a postfix/smtp[3684]: 6B47641AF2: to=<anyuser@true-destination.com>, orig_to=<anyuser@alias-destination1.com>, relay=10.0.0.245[10.0.0.245]:2525, delay=0.03, delays=0.01/0/0/0.02, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 705AA40459)
Apr  6 22:39:43 smtp-a postfix/qmgr[3681]: 6B47641AF2: removed

recipient_bcc_maps = pcre:/etc/postfix/forward_bcc.pcre

/^user@olddomain.com/ user@newdomain.com