==== Required information ====
- iRedMail version: iRedAdmin-Pro v1.5.1 (MySQL)
- Store mail accounts in which backend: MySQL
- Linux/BSD distribution name and version: CentOS 6.3
- Related log if you're reporting an issue:
====

Hello,

I've run into a bit of a challenge. The "owner" of one of the domains I host on our iRedMail installation has made a deal with a local mobile telco for a private APN for their smartphones. This telco *requires* that these smartphones deliver their email at the telco's own SMTP server (authenticated).

So these users send out email, with a from address in a domain hosted on our iRedMail installation, via the telco's mail server. If they try to send an email to themselfs, it will arrive at iRedMail, and it will reject it with "not logged in", as it detects it's a local user, and there was no SMTP authentication.

Obviously I don't want to disable this for the entire server (that would effectively make it an open relay), but I would like to allow users for this particular domain (and this domain only) to use the telco's SMTP server for outgoing email, and have iRedMail accept these emails.

Any idea how this can be configured?