[Fetchmail-users] Working around "Bad sender address syntax" error?

[Daniel B. <dba...@bl...>]

I use fetchmail to retrieve email from an IMAP server every five
minutes, passing it to a local postfix process on my home Linux box
for delivery. The problem: sometimes an email has an invalid "From"
line (usually spam), like this one with leading hyphens:

  From: "- Some Dumb Spammer" <-Du...@ex...>

In this case, when fetchmail retrieves the email, the local postfix
process raises an error:

  fetchmail: SMTP error: 501 5.1.7 Bad sender address syntax

This error causes fetchmail to leave the bad email sitting on the IMAP
server, even when my .fetchmailrc file specifies "nokeep". As a
result, fetchmail re-downloads it every five minutes. Repeat
forever... or until I manually delete the bad email from the IMAP
server.

What's the best way to break these loops automatically, either
deleting or delivering the bad email, without opening a security hole
(e.g., permitting leading hyphens)?

Thank you very much.

--
Dan Barrett
dba...@bl...