I had in fact already contacted BT directly but it took a while for the complaint to be taken seriously. Tenacity eventually paid off and they did listen to my complaint that email was being put into the spam folder even though the sender was in my safe senders. They couldn't resolve the problem but then I hit on the word "escalate", and they did indeed duly escalate the issue to the next tier of help and that is where we are, still working through some issues that I will report on when there's more to say.
What has happened so far is that about 10 days ago, long enough to see if it really has had an effect, they made a change since when neither I nor my wife have had any email going into the spam folder from senders already in our individual safe senders. This is a positive step. We have both had email arrive in the spam folder, but always* from those not in our (individual) safe senders - some has even been actual spam!
I've tried to get them to tell me if the change is a generic one that will benefit everyone or if it has been specifically targeted at just our mailboxes (surely not!). Perhaps some of you who have been experiencing the same could check if email coming into your spam folder comes from addresses already in your safe senders.
* I say always but one of the quirks currently being investigated is that emails from 2 particular addresses (in safe senders) keep getting moved to spam no matter how often I mark them as not spam and see them migrate to the inbox. A short time later (not immediately) they reappear in spam. The is the first of the other things on the list to be investigated.
Since it has been escalated I've been reasonably impressed with the seriousness with which they are treating the issues.
I'll report more as there are developments.
