The other day I recall someone mentioning they routinely block anything where the mailer is MIME::Lite. I don't do this myself as any self respecting spammer with more than a quarter of a brain cell is not going to make a slip like that {a script kiddie may - but that is another story}.
I noticed this morning that Hampshire County Council use it, and I expect it is part of a 'solution' that many County Councils and Government Bodies use in the UK: X-Mailer: MIME::Lite 3.021 (F2.74; T1.21; A1.77; B3.07; Q3.07) Date: Thu, 30 Jul 2009 14:12:19 +0100 From: xxxx...@hants.gov.uk So beware if you are blocking on Mailer Type MIME::lite !