Matt Fretwell wrote:
Bart Silverstrim wrote:
Maybe even do a reverse check to see if there's a mail server on the
sending system...how many systems would break doing a check like that?
The sending server isn't guaranteed to be a MX, so any DNS MX or reverse connection tests would fail.
But that doesn't mean you can't connect to an MX for the sender's domain to confirm they exist -- that you could send mail *to* them. This is a fairly regular check some mail systems perform. I was amused by one recent system that did this against my MX but did it from a host with a name that didn't match it's IP address, so mine rejected it... haha
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