Getting TMPTITLE every 30 min

Start by logging into the email account Postie is checking. It likely has an email with a large attachment or many attachments. If so try deleting the email or increasing the amount of memory allocated to WordPress. https://postieplugin.com/fatal-error-out-of-memory/

If that isn’t the issue try installing the Support addon and sending the logs to [email protected]
https://postieplugin.com/downloads/support-addon/