This configuration has been submitted by a Gradwell user, and is not supported by Gradwell technical support at this time.
trixbox has the functionality to alert users via email of waiting voicemail, this function needs to be configured via the trixbox web admin panel.
Some users of trixbox have port 25 blocked by their ISP, which will affect the sending of emails. See the following article http://dumbme.mbit.com.au/trixbox2/trixbox2_without_tears.pdf.
Remove the entry in the etc/hosts file referencing your server.
Remove Sendmail and Install postfix
rpm -e --nodeps sendmail
yum -y install postfix
Following this, edit your /etc/postfix/main.cf, (use nano and my smtp server is shown below, but you should be using yours) and add:
relayhost = smtp.ozemail.com.au
Replace smtp.ozemail.com.au with your own smtp server. E.g. if your belong to OPTUS,
it should be:
relayhost = mail.optusnet.com.au
You should also edit /etc/asterisk/vm_general.inc and set the "serveremail" parameter to your real email address.
This is to avoid messages with invalid from-addresses floating aimlessly in the Internet.
Then load Postfix.
service postfix reload
Postfix will now send all outgoing email to your ISP's mail server.