ColdFusion Muse

FQDN for Mail Servers

In this previous post detailing how to manipulate mail headers there was some lively discussion as to whether this was really ethical or not. Just today CF Guru Brian Rideout mentioned that he was having trouble getting ColdFusion mail past a declude filter (a common spam filtering technology supported by many mail servers) due to the mention of ColdFusion in the mail headers. Brian came back and indicated it was actually something else - and his tip bears repeating.

When you specify an email server, either in the CF administrator or in the cfmail tag, make sure you use a fully qualified domain name. It is not advisable to use an IP address here. Remember that many IP addresses you might use are actually "internal" to your network and not public IPs (like or or even When you think about it, it makes sense that declude would hold an IP address against you. It would expect mail to come from a public server. In fact, there are many technologies that analyze the origin - spf, dkim, reverse lookup etc. So make sure and use a real FLQDN - even if you have to edit the hosts file on the server to get it to resolve :).

Eric Cobb's Gravatar To me, this seems like it would be a problem with your mail server, not CF. The mail server is responsible for telling the world the FQDN the email is coming from, not CF. All the mail server settings in the CF Administrator do is tell CF who to pass the mail to so it can be sent, right? The mail server does the actual sending of the mail, and should have everything set up to report its FQDN. So if you specify the mail server's IP address in the CF Administrator, that should be fine since the mail server itself is the one actually sending the email. All CF needs to know is which machine to pass the mail to so it can be sent.

I may have a misunderstanding of how things work, but CF isn't a mail server, it just connects to one and lets it do its job, right?
# Posted By Eric Cobb | 2/13/09 1:49 PM

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