I received three substantially identical emails beginning
"Hi,
I took a look at your site a couple of hours ago...
and I want to tell you that I'd really love to trade links with you. I think
your site has some really good stuff related to my site's topic of (topic)"

(topic) is different in each of the messages, "radar detectors",
"driving school", and "criminal records"; these are vaguely related
to my page http://www.mit.edu/~jfc/laws.html about traffic law.
The mail goes on to say that the site links to mine and invites me
to put a reverse link on my page to www.(topic)hq.com. Obviously
the text is a computer-expanded template but the placement of the
links to my site seems to have been done by computer rather than
manually.

The body is base64 encoded plain text which makes me think there is
an attempt to get past a filter.

What's up with this? Legitimate directory site, attempt to trick
search engines, or something else? I'm asking here because I'm
betting on the second, and I wonder if this sort of trick is common.

--
John Carr (jfc@mit.edu)