==== Required information ====
- iRedMail version (check /etc/iredmail-release): 0.9.4
- Linux/BSD distribution name and version:  Debian 8.3
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Apache
- Manage mail accounts with iRedAdmin-Pro? Yes
- Related log if you're reporting an issue: Sender address rejected: not logged in
====

Hi.
We have a fully working release of IredMail with IredAdmin-Pro.
We accept mail from internet on 25 for the domain and our client send mail with auth on port 587 like documentation.

Our customer have bought sophos appliance (antispam/AV) and we configured it like MX on DNS for our domain, sophos appliance routing all mail to our iredmail server.

After this step all mail on iredmail server are rejected:
553 5.7.1 <user@domain>: Sender address rejected: not logged in (in reply to RCPT TO command)

INTERNET ---->  (25) SOPHOS MX ----->  (25) IREDMAIL ---- USER

Any idea how resolve problem?
Best Regards