==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release):
- Deployed with iRedMail Easy or the downloadable installer? installer
- Linux/BSD distribution name and version: centos 7
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): AD 2012R2
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? no
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

This is more the solution that anything.

For a few months now, an install of iredmail was giving me a lot of issues. Everything worked well for over 1 year and 1/2 and the all of a sudden, amavisd started to block legit emails with .emz extensions. searched the amavisd file a lot but could not find any entry with .emz.

This evening just found the solution.

It must be an upgrade that changed the # in the amavisd file so the following line need to be commented

$banned_namepath_re = new_RE(
    #[qr'T=(rar|arc|arj|zoo|gz|bz2)(,|\t)'xmi => 'DISCARD'],     # Compressed file types
    [qr'T=x-(msdownload|msdos-program|msmetafile)(,|\t)'xmi => 'DISCARD'],
    [qr'T=(hta)(,|\t)'xmi => 'DISCARD'],

mine was line 670

    #[qr'T=(rar|arc|arj|zoo|gz|bz2)(,|\t)'xmi => 'DISCARD'],     # Compressed file types

This not commented will see .emz which is Windows Compressed Enhanced Metafile file and either drop or quarentine it as you would have set.

Hope this will help someone else in future

Rajbps