Hi Rhys,
Which build of NT7 are you on?
You'll need to be on 7.40 in order to use TLS1.1 and 1.2. Before that it only goes up to TLS 1.0.
The other thing about NT7 is that you can set the SSLMethod specifically to NET:SSLMethodTLSv1_2.
The default in NT7 is NET:SSLMethodTLSv1 - ie TLS 1.0, not 1.1 or 1.2.
>> The NT doco says that it tries different TLS settings until one works
The default in NT8 and later is NET:SSLMethodTLS but this isn't available in NT7.
With NET:SSLMethodTLS it attempts to connect on TLS1.2, then 1.1 then 1.0. , but as I say that's only in NT8.45 or later.
Back to Outlook - the most likely issue is that they may have changed the minimal SSLMethod they accept. So try setting the SSLMethod to NET:SSLMethodTLSv1_2 and see if that helps.
Cheers
Bruce