the direct mailer in zope.sendmail can fail in the second phase of 2-phase commit.

[Jim Fulton]

If an error occurs when sending mail using a direct mailer, then the error occurs during the second phase of 2-phase commit. This is considered a critical failure by the transaction system. A properly-deployed production application should wake people up when critical errors occur.

Transactional email is, at best, a compromise. It would be better, however, to generate errors during the first phase of two-phase commit.

(Arguably, it would be better to use queued mail and have some out-of-band channel to get errors back to the user. Unfortunately, no such channel exists currently, and would be somewhat tricky to use if it did exists. Queued-mail without a mechanism to notify users of errors is unacceptable if actually delivering mail is important.)

A simpler fix is to swap tpc_finish and tpc_vote methods in zope.sendmail. The hard part is writing the test. :)

[Colin Watson (cjwatson)]

The zope.sendmail project on Launchpad has been archived at the request of the Zope developers (see https://answers.launchpad.net/launchpad/+question/683589 and https://answers.launchpad.net/launchpad/+question/685285). If this bug is still relevant, please refile it at https://github.com/zopefoundation/zope.sendmail.