Automatic mail processing not working

Automatic mail processing stopped working from Dec 18th. I can update the posts by clicking on “Process Email”. Hence, the link to the email is not the problem.

Postie is up-to-date and was not recently updated so that can’t be a problem with a recent update.

I have checked and the CRON settings are not a problem:

DISABLE_WP_CRON: Off
ALTERNATE_WP_CRON: Off
WP_CRON_LOCK_TIMEOUT: 120

What else could be the problem? How can I debug this?

Thanks.

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