I have searched and got nowhere so far. Running Drupal 7 on Debian Wheezy with postfix.
Sendmail works from the command line. Pasting a basic PHP block into a page which sends an email works fine. Contact forms or webforms cannot seem to successfully send mail.
I have tried setting up the SMTP module with no change in success rates.
No errors are appearing in /var/log/mail*
Drupal logs just say "error", unless there's a more verbose log I have yet to find.
This is my first Drupal install.