[exim] SMTP command timeout for every message, even on succe…

For every email my application sends I get an "SMTP command timeout on
connection from localhost" error. This makes sense with what I've read
in the docs because if I have my application send an email and then
immediately run "exiwhat" the output shows that it's handling an
incoming connection from localhost and it stays that way until it
times out after 5 minutes.

It's doing this even upon successful message delivery. That is to say,
I can send an email, exim will deliver it, it'll appear in my inbox,
and yet exiwhat output still shows that it's handling a connection.
And, after 5 minutes I'll get the timeout message in the logs.

Clearly I have something misconfigured. Any thoughts as to what could
be causing this? Is it a problem? Messages seem to be delivered fine.

Thanks.