I am having a problem with forum digests not working, generating digests only results in the following error message for the cron job (one line for each user its trying to generate it for):
"ERROR: mod/forum/cron.php: Could not send out digest mail to user 1234 (mail@example)... not trying again."
If i change user setting to "no digest", people do receive mails as they should.
Checking the logs from the mail relay we have sitting between moodle and the mailserver, shows moodle doesn't even try to send the digests, so the error seems to be within moodle.
The cron job doesn't run out of memory or times out, as i get a "Scheduled task complete" after the job with statistics of the process.
I have tested on both moodle 3.15 and 3.2.2.