[exim] Exim problem with non-TLS supporting senders

I've some users that cannot receive emails from a particular domain.
On checking the logs, I see massive ton of incomplete transaction like
this

incomplete transaction (connection lost) from <xxx@xxxx> for yyy@yyy
unexpected disconnection while reading SMTP command from ()

Running a mxtoolbox.com check on the other server seems to point to
the fact the sender's server does not support TLS.

I'm reluctant to disable TLS on exim just because of one sender so
wondering what is the best way to handle such senders?