Exim logs /var/log/exim_mainlog shows Berkeley DB error.
Berkeley DB error: PANIC: fatal region error detected; run recovery
Berkeley DB error: PANIC: fatal region error detected; run recovery
Berkeley DB error: PANIC: fatal region error detected; run recovery
Exim stores certain databases using BerkeleyDB (e.g. aliases file). These are due to corrupted Berkeley DB.
In cPanel server you can remove / move the DB and restart exim to fix.
mv /var/spool/exim/db /var/spool/exim/db.bak
/scripts/restartsrv_exim
Now confirm the errors are gone.
tail -f /var/log/exim_mainlog