I've run into a sort of problem with the emailing functions on our Drupal (5.7) site. It's hard to say when this arose, since we don't use these features much.
The problem was discovered when my boss tried to email an OG group, as she sometimes does, and after clicking "Send email" was taken to "Page not found". Further testing demonstrates this is also a problem sending emails via user pages and the site-wide contact form. Actual receipt of sent emails appears to be intermittent, which doesn't help. The "Page not found" error, however, is 100% consistent. The only evidence in the Log appears to be the 500.shtml "page not found" notification with a URL such as ".../user/3/contact http://www.t4tcolorado.org/user/3/contact". The logged URL works until the email form is submitted.
As we don't use this feature often, it's possible this occurred when I moved from 5.5 to 5.7 and it wasn't noticed. That said, I'm not even sure where to look. Thanks for any pointers,
Brian