TLS connection died

Hi all,

we have a mail in the queue that won't go out with the following error from the send-current log:

TLS_connection_to_65.55.37.88_died:_error:00000000 :lib(0):func(0):reason(0)/

The mail should be going to outlook.com, but since the error code is a bit, ahm, empty, I have no idea what could be the cause.

Any ideas?