Thanks, Martin. Yes, this seems to be a problem. Many places seem to be OK with just looking up sift.net, but cl.net is one of a handful that won't accept that and need the mail address to line up exactly with mail.sift.net.

I've reported this to our sysadmins and they are trying to figure out a solution.

On 22 Jul 2020, at 5:44, Martin Simmons wrote:

On Wed, 15 Jul 2020 11:22:51 -0500, Robert Goldman said:

By the way, this is not my normal email, but emails from my work address
(rpgoldman@sift.net) are being bounced because of the reverse lookup
policy on common-lisp.net.

It seems to be puking on this:

Your IP address 50.249.120.161 is associated with the domain sift.net.
Nevertheless your message appears to be sent from mail.sift.net.

I think SIFT has misconfigured reverse DNS:

# host -t a mail.sift.net.
mail.sift.net has address 50.249.120.161
# host -t a 50.249.120.161
161.120.249.50.in-addr.arpa domain name pointer sift.net.
# host -t a sift.net.
sift.net has address 50.249.120.162

The reverse DNS for 50.249.120.161 should be mail.sift.net. for best practice
(see https://www.debouncer.com/reverse-dns-check?ip=50.249.120.161).

__Martin