Postfix

Tried that. Won't work. Here are my settings in outlook express for the users on the mail server that I would like trixbox to be on. I created an account called trixbox on the server.
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Outlook setting under servers tab:
Server Information---------------------------------------
My incoming mail server is a POP3 Server.
Incoming mail(POP3): mail.XXXXXXX.com
Outgoing mail (SMTP): mail.XXXXXXX.com
Incoming mail server------------------------------------
Account Name: trixbox@XXXXXXX.com
password:*****************
Remember Password: (checked)
Log on using secure password authentication: (unchecked)
Outgoing Mail Server------------------------------------
My server requires authentication: (checked)

Outlook express settings under Advanced tab:
Server port numbers------------------------------------
Outgoing mail (SMTP): 26
This server requires a secure connection (SSL): (unchecked)
Incoming Mail (POP3): 110
This server requires a secure connection (SSL): (unchecked)
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These are all of the settings in Outlook express to be able to send and receive mail through the account. I put in the server, the port, the username , and the password into the trixbox general settings and hit save. Then I went in and did what the above link says to do and it still does not work. Is there something that I am doing wrong?

Thanks

I could be wrong but I see Trixbox 2.8 also installs sendmail so maybe you need to configure sendmail.