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Old 06-05-2007, 05:22 PM   #1
Registered: Oct 2004
Location: Merrimack, NH
Distribution: Ubuntu / Apple
Posts: 46

Rep: Reputation: 15
Sendmail and SMTP relay + Asterisk

Heya everybody,

Let me give a quick overview of what I am doing here. I have an A server running Linux (CentOS) and Asterisk. There are a few other services running to support it such as Apache, OpenSSH, Sendmail, etc. This server accepts all of our analog phone lines, and creates a phone system that our internal IP phones can connect to.

What I am now setting up is a simple system that emails and/or pages one of our employees when they recieve a voicemail message. Asterisk is built to do this by default - it simply uses Sendmail to send mail from itself (Which by default is something like asterisk1.local, I have reconfigured this to be our own domain and hostname). For the most part, this works just fine - Problem is, since it is sending messages directly, some of the emails are being rejected - for example if an employee wishes to have the alert sent to a Comcast account. It is being rejected because the server is behind a firewall on a NAT, with a 192.168.x.x address. The Comcast server will see the address of our NAT, which reverses to something like - So naturally, the connection is rejected

What I need to do to make this work, is force the server to relay mail through my existing mail server - which is This server requires SMTP authentication even if the domain is local, and several other security measures. Because this server has its own fully routable IP, and a proper reverse to go along with it, it has no issues sending messages.

So to simplify my ranting - I need to know how to make Sendmail relay through another existing email server - this server will require SMTP authentication credentials to be provided by the Asterisk box running Sendmail (I believe it is often refered to as a "smart server")

Thanks a bunch,


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