[Mimedefang] md_check_against_smtp_server() returned an empty response

Richard Laager rlaager at wiktel.com
Wed Mar 27 04:41:17 EDT 2013

This is unrelated to the other thread.

I'm troubleshooting an issue where md_check_against_smtp_server()
intermittently hangs for 5 minutes. It's *always* 300 seconds exactly
(ignoring sub-second precision).

The error is always the "returned an empty response" from

I'm using this function for doing callbacks against the sender's
address. I look up the MX records using Net::DNS. Before you hate me too
much, I cache positive responses for 7 days and negative responses for 1
hour. The delays discussed above are around the actual
md_check_against_smtp_server() call and *nothing else*. To get this far,
I had to instrument my filter with logging before and after every
non-trivial block of code.

Does anyone have any idea why the 15 second IO::Socket::INET timeout
isn't applying in these cases?

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