It is possible to set the default in the ACP but uses can override it in their settings.
Digest emails not getting sent
I had a similar issue, and found out it was related to email throttling.
The mail server rejected most of the digests, as they came in too fast.
If this is your issue, there is a solution, but it needs to be integrated into the main code.
Follow my comments here:
I ran into a similar issue this weekend when the digest tried to run.
The issue that I have is that SparkPost automatically adds emails to a restricted list when they bounce or get reported. When NodeBB attempts to send a message to one of these email addresses, an error is thrown and at some point the whole process stops sending. In addition to throttling, it would be nice to ignore the email failures like this and continue.
@baris If I change the cron job to run the weekly on a different day (today) and it's been less than a week since the last attempt (Sunday), will the people who were already sent a weekly digest (on Sunday) be sent another weekly digest? I don't want to spam those first 1000 people.
They would get it again I believe.
Darn, that makes debugging difficult. I guess I'll file a bug with the errors that stopped the digest send.