Hello Zhang

==== Required information ====
- iRedMail version (check /etc/iredmail-release):  0.9.7 MYSQL edition
- Linux/BSD distribution name and version: CentOS release 6.9 (Final)
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MYSQL
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====

https://www.python.org/dev/peps/pep-0257/ specifies using the """ in the docstring.
However, I see many places where the 3 double quotes are used that are not docstring specific.
run the below to seereferences when the """ is used when assigning a value to a variable.
       find /opt/iredapd/ -type f -exec grep -HI '"""' {} \;|grep "="

I'm new to Python, and from what I can tell this is not proper. I'm also not quickly able to ascertain how such quoting is handled by Python for example:

    sql = """SELECT accesspolicy
               FROM alias
              WHERE address='%s'
              LIMIT 1""" % (mail)

Perhaps you can provide some insight as to why VAR assignments have the 3 double quotes.

Sidenote;
I'm trying to understand a variety of things with iredapd, and was led to notice this while reviewing why the records in vmail.forwardings do not seems to every match up with any possible return from the catchall_maps.cf, that is specified in main.cf for virtual_alias_maps variable.