[exim] MySQL Connection errors – SSL?

Hello everybody.
I'am using MySQL for several lookups and everything worked fine for many
years with a „5.0.32-Debian_7etch12” MySQL Server. Today I switched the
backend to „10.2.14-MariaDB-10.2.14+maria~xenial” and everything seemed
to work fine again at first. But then I checked the logs and found these
connection errors on the SQL server:

Aborted connection 17263 to db: 'XXX' user: 'XXX' host: 'XXX.XXX.XY'
(Got an error reading communication packets)

These errors seem to appear for every request. On the other hand Exim
shows no errors so far – everything works fine and Exim has no lookup
errors. tcpdump showed no obvious problems.

So, my questions would be:

1. Does Exim close the MySQL connection properly? One explanation I
found suggested that this could pose a problem.

2. Is there any other possivle explanation for this behaviour?

3. Are there any SSL related configuration options? My new server has
ssl configured but the Exim documentation shows no options for this.

best regards,
Kai