SPF, DKIM signature and DMARC Policy and other headers such as list-unsubscribe (for mailing lists) are taken into account to work out email reputation along with blacklists and the content/body.

For personalised mass emails I use python with Mailchimp APIs, office365 mail servers and setting headers such as list-unsubscribe and list-unsubscribe-post and ensuring emails are appropriately signed and checking DMARC reports.

Well thanks to everyone for the replies.

Trying to draw it all together, it looks as if for normal social use by a domestic customer then btinternet.com have a vice-like grip and there is nothing the sender can do to alleviate the problem. One or two of the recipients for my weekly e-mails have supplied me with alternative addresses from the likes of gmail or hotmail but that is a step too far for other users who have always used the GPO for their phone and who have just added internet to their decades old relationship.

Is it just me, or is the current btinernet.com policy another reminder that below the surface of the BT lagoon there still remains a lot of the old nationalised industry mindset?

In reply to a post by GonePostal:

In reply to a post by jabuzzard:

In reply to a post by John_Gray:

Those who wouldn't or couldn't, we had to sent out individual newsletters to each person's BT-email-address as the only addressee.

Noting in 2020 if you don't do that then well nice GDPR violation for you.

A lot of postings going out using bcc are in big trouble then.

Nope. A bcc email is a bunch of separate emails under the hood, one per recipient on the bcc: list, plus one more if there is a to: or cc: recipient.

A large number of people sending out newsletters have a tendency to put everyone on the to: or cc: which is a GDPR violation. Well unless you have their explicit permission for that which is highly unlikely.

In reply to a post by jabuzzard:

A large number of people sending out newsletters have a tendency to put everyone on the to: or cc: which is a GDPR violation. Well unless you have their explicit permission for that which is highly unlikely.

Not wishing to undermine the importance of the point, but any violation depends on the scope (i.e. is the newsletter a personal update or an update from a formal or informal organisation). For example, quoting from an internet report copyright University of Gottingen, " . . . the GDPR does not regulate the processing of personal data that natural persons carry out as part of purely personal or household activities, for example, correspondence and social networking." It is not necessarily a GDPR violation (although not necessarily best practice) to use to: or cc: rather than bcc:

In the case of the blocked e-mails that started this thread, I use bcc: as a matter of best practice but I would assume that an update about an informal competition among a group of social acquaintances would fall outside the GDPR regulations.

In reply to a post by GonePostal:

In the case of the blocked e-mails that started this thread, I use bcc: as a matter of best practice but I would assume that an update about an informal competition among a group of social acquaintances would fall outside the GDPR regulations.

I believe you are correct as I understand GDPR (aka, UK Data Protection Act 2018)