======== Required information ====
- iRedMail version: 0.9.0
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Apache
- Linux/BSD distribution name and version: Ubuntu 14.04.02 (Lubuntu on Banana Pi)
- Related log if you're reporting an issue:
====

I've seen several queries about email address aliases based on a regular expression several times, but no real answer other than "create an alias for each possible address" which won't work for me.

What I needed was for anything that started with, for example, "foo." to be redirected to "foo@example.com".  So if I wanted to sign up at, say, Costco, with an email address, I could use "foo.costco@example.com" and it would go to my real address of "foo@example.com"

I made some simple configuration changes to make this work:

1) First I added an "isregex" column to the alias table:  ALTER TABLE alias ADD COLUMN isregex TINYINT(1) NOT NULL DEFAULT 0;

2) Next I created a new file, /etc/postfix/mysql/virtual_alias_maps_regexp.cf.  Most of this is the same as all the other files in the directory.  The difference is the "query" line:

query = SELECT alias.goto from alias,domain WHERE '%s' REGEXP CONCAT('^',alias.address,'$') AND SUBSTRING(alias.address,1,1) != '@' AND alias.isregex = 1 AND alias.domain='%d' AND alias.domain=domain.domain AND alias.active=1 and domain.backupmx=0 domain.active=1

3) add a reference to the above created file to the virtual_alias_maps entry in /etc/postfix/main.cf file.  I added it between the entries for "virtual_alias_maps.cf" and "domain_alias_maps.cf".  The part I added was:

proxy:mysql:/etc/postfix/mysql/virtual_alias_maps_regexp.cf,

4) Finally, I inserted the new alias into the database:

INSERT INTO alias (address, goto, domain, isregex) VALUES ('foo\..+@example.com', 'foo@example.com', 'example.com', 1);

This alias matches anything that starts with "foo" and a dot, followed by one or more other characters and then @example.com.

And it all works.  Now I can use emails such as "foo.costco@example.com" and "foo.bestbuy@example.com" and I can know who is selling their contacts to spammers.  BTW, the reason I don't want to just use "costco@example.com" and "bestbuy@example.com" is because I might have different users each using their own aliases:  "foo.costco@example.com" and "bar.costco@example.com".