It's hard to remember that everyone doesn't have 7+ Gb of email storage. If I wanted to use a service like this, I can't imagine an email with the fulltext of a listing being big enough to ever bother me.
Giving your users the option to only receive links can't hurt, though.
one email is not a problem, its getting 40 emails a day
Re:Ask HN: Review my web app, CraigUpdate.com
by sil3ntmac on Friday July 17, 2009 @05:45PM
(#710862)
The emails sent out are short (around a paragraph), and every email that is sent to you has an 'unregister' link at the bottom that you can click and you will stop receiving emails regarding that search result.
How about adding results to a special anonymized (not password protected, because they can't really handle it yet) RSS URL?
or are you doing the smart thing and just sending people a single email "We've found a new match" with a link to the craigslist search results, sorted for their search preferences?