Ady,
Thankyou for the information.
I have checked with my friend this morning and, he has emailed my TalkTalk email address, and his emails do now seem to be getting through. Hopefully this is a sign that the block has been removed.
My friend has also checked his inbox, spam and deleted items folders and confirms that he is not getting any unknown bounce-back messages, which you would normally expect to see if his Gmail address was being spoofed to be used for sending unauthorised mass spam messages.
My friend confirms has has a strong password on his account, including 13 characters, with a mixture of lowercase, uppercase, numbers and symbols. We have agreed as a precaution he will change this again, just to make sure there is no unauthorised access.
If I had to speculate, I know that my friend does voluntary work as a club secretary for an amateur vintage motor club, which involves sending "circular" emails to fellow members from time to time, which he does by using of the usual blind copy list to maintain individual member privacy (in accordance with GDPR). The blind copy list is generally in the order of 100 verified personal email addresses, so I wonder if this is what the TalkTalk spam filters might be picking up on? If this is the case I and he, would be grateful if the filter can be "trained" to accept that his messages in this format are not spam.
I note that although the intermittent block is not a particular problem to me for his normal messages between us, because I have alternate email addresses that we can use, he has other email recipients who seem only to with to use TalkTalk email addresses (exclusively), and this causes significant distress when messages are blocked. Anything that you can suggest to mitigate future problems with false spam tagging would be appreciated, other than the obvious, which is to beg his other recipients to change away from using TalkTalk email, if they want to stay in contact!
Many thanks, again, for your help in this matter.
