SMTP relay to my ISP stopped working?

A couple of day's ago I noticed that no emails was leaving my system ...

I'm using a transparent SMTP Proxy on Sophos UTM  9.411-3, running on a Hyper-V

This is how the smtp.log looks like when is not working:

2017:03:11-01:16:51 sophos-utm1 exim-out[6957]: 2017-03-11 01:16:51 1cmUiI-0001o9-D3 => -masked-@gmail.com P=prvs=0243f58e52=private@mail.adress R=smarthost_route T=smarthost_smtp H=smtp.bredband.net [195.54.106.231]:25 A=server_plain C="250 ok:  Message 1117530659 accepted"
2017:03:11-01:16:51 sophos-utm1 exim-out[6957]: 2017-03-11 01:16:51 1cmUiI-0001o9-D3 Completed

This is how the smtp.log looks like when is working:

2017:02:24-20:21:11 sophos-utm1 exim-out[38108]: 2017-02-24 20:21:11 1chLQU-0009uZ-4v => masked@mail.adress P=prvs=0228dae88a=private@mail.adress R=smarthost_route T=smarthost_smtp H=smtp.bredband.net [195.54.106.231]:25 A=server_plain C="250 ok:  Message 1108372053 accepted"
2017:02:24-20:21:11 sophos-utm1 exim-out[38108]: 2017-02-24 20:21:11 1chLQU-0009uZ-4v Completed

Both gives me a 250, message accepted, both since 1 day no emails is delivered
If I disable transparenr Proxy and test username and password in Thunderbird, it works?!

Any idea would help, have been browsing the forum for any new angle ...