Does a GAE app keep a log of the emails it sends?
you can try one of the following way:
Log

write a log to datastore while each time you call sent_mail. 
write log with logging module and check the log in dashboard.

mail

while send the email, add a debug email address in email's "bcc" field. 
you can also check the "sent mail" in the email account used as sender.
Wondering if it is possible to see a history of emails that a GAE app has sent? Need to look into the history for debugging purposes.
Note that logging when I send the email or bcc'ing a user are not options for this particular question as the period I'm curious about was in the past (since then we are bcc'ing).