Have you restarted qmail and if not resolved, have you restarted server
It could be because TLSv1 has been stopped in latest version, and if host your connecting to requires TLSv1 then I guess it would fail (not on all email sending though, as there will be a mix of v1 v1.1 and v1.2)
This is a quick fix though, as you need to create a file called TLSCiphers I think but I will look up the exact thread and post for you
If all fails, I would open a support ticket with your license provider
Since I did that, no messages have been deferred and the obscure “TLS_unable_to_load_control/tlshosts//_” message no longer appears in the logs. Naturally, I’ll need to monitor it for a longer period before I can say whether the issue is permanently fixed.
However, I don’t really understand why the above apparently fixed the issue and what other (if any) consequences changing the ciphers to those shown above would have, which makes me a little bit cautious.
I’ll update this thread in a day or two to let you know if the issue returns or not.
It could be the TfL?s protocol or looks more likely to tight ciphers. It looks like you relaxed them but RC4 ciphers I thought we?re not meant to be used any longer. Sorry maybe thinking of something else