Asterisk/Trixbox and SENDMAIL question

Hi - this may be kind of a bizarre question but here goes…

I’ve been using Asterisk/Trixbox for some time now. I’ve always used the e-mail notification feature when a new message is left for a voice mail user with no problems.

Recently, we’ve changed our ISP to Comcast high speed cable with no problems except one…

It seems that no e-mail notifications are being sent out anymore or if they are, Comcast mail servers are rejecting them. We use Microsoft Small Business Server 2003 and here is what I have discovered.

I have my exchange server connected directly to the Comcast Cable modem so that outgoing/incoming e-mails (to server users) are sent via DNS. The Trixbox is installed behind the server but has it’s own private IP address, i.e. I have configured the Nameserver in Trixbox to match the Comcast DNS and have tried other variations as well.

After doing a lot of testing with sending test e-mails to myself, here is what I’ve found:

Comcast will not allow me to relay emails directly from their Cable modem connection to other Comcast users. I get a rejection e-mail stating this.

I have tested sending an e-mail from my SMall Business Server e-mail account to another Comcast user and it was returned. For whatever reason, I cannot send e-mails (via Server or otherwise) directly via DNS. However, when I re-configure my Small Business Server to direct outgoing e-mails to Comcasts mail server, i.e., everything goes through fine with no probelms.

I believe this is the problem I"m having with Trixbox and why it is not sending voice mail notifications. Does anyone know how I can re-configure SENDMAIL (or whatever application is responsible for sending e-mails outbound) to relay outgoing e-mails to as opposed to sending out via DNS???

Thanks for any help you can give…

This is possible. I don’t have my config files with me (they’re at the office), but if you remind me tomorrow, I can look up which files/settings you change within the sendmail settings to specify an alternative MTA.

Most ISPs now are blocking any kind of external port 25 access, which basically means no SMTP access outside of their own specified mail servers. Usually, you can call them and they’ll unblock it for you, especially if you have their business packages. That’ll remove the need for you to have to specify any kind of external MTA at all, and you’ll just be able to let sendmail do it.

Called Comcast and since I’m not under their business package, they will not unblock.

Any additonal help will be appreciated.

What you can do is have sendmail relay it off of comcast’s server.

The file you need is in /etc/postfix/ . Add a line:

relayhost =

I’m not sure of the configuration should you need to authenticate for, but you shouldn’t if you’re coming from a comcast IP.

you cannot just open relay without permission. that ended years ago with the spam surges and the advent of real time black holes. so simply setting the will not work.

your config changes will lead to mail going to comcast server but the comcast server will reject it.

if comcast, or any other ISP, will not relay because you do not have the right package, you have to send direct. to do that and have recipient servers accept your mail, you need to make your box compliant on the internet with current mail server standards [valid domain and valid MX record in the domain that matches the mail it is sending etc]. This can be done [free] using dyndns.

There are other workarounds but they get more complicated to set up [e.g. setting sendmail so that it logs on to comcast using your mail credentials before relaying].

No, this is the problem exactly that he is having. He cannot send directly to the recipient servers because Comcast blocks outbound port 25 access to all but their own email servers.

Thus, he needs to relay the email through Comcast’s email servers themselves. He’s on Comcast’s cable service, so the email servers are generally configured to not require authentication for a Comcast IP address, thus he should be able to relay off of them without issue.

I had posted something a few months back about setting up Postfix for “authenticated email relay”.

Most email servers will allow email relay, as long as the user of the service is authenticated as a subscriber.

Check here for details.