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Sendmail is configured to forward through a smarthost at AWS. The smarthost DNS only advertises ipv4 addresses. When Sendmail looks up the address, for some reason it has decided to return the ipv6 address of my server, thus resulting in a loopback issue.

I tried setting CLIENT_OPTIONS for ipv4 only, but that didn't work.

I eventually resorted to hardcoding an IP for the AWS server into my /etc/hosts file, but that obviously is problematic.

How to I tell Sendmail that if there is no ipv6 address in the DNS to use the ipv4 address? Or could it be a DNS resolution configuration error?

Has anyone else encountered this?

MJP
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1 Answers1

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I was able to track down the issue and solve it.

Many years ago, I added a CNAME to my domain pointing * to www. It was one of those tricks to make it so that typos would automatically go to the web server, which is in general what I wanted at the time. In this case, it was causing the the resolver to return the IPv6 address of my web server instead of the IPv4 address of the smarthost.

Removing the CNAME fixed the issue. Of course, since it's been in there for many years, I can't wait to find out about everything that just broke.

MJP
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