I am new to this community and do not have a btinternet.com email account. I am trying to help a group of btinternet.com users. I am the Email-Coordinator of a club with round 100 email users on our distribution list with all manner of email addresses.
For the past 20 years I have been sending regular emails to all members by sending two similar emails (surnames A-L and M-Z) each containing around 50 members in the BCC block, this has worked perfectly. Our emails go out from a long-standing gmail account using Thunderbird on Windows 10 with our club's nickname and topic in the Subject entry.
Since mid-August 2024 my 20 btinternet.com email users have been receiving corrupted emails, all other users are receiving the emails as normal. The corruption is in fact, at least looks to me like, the usually invisible HTML coding appearing as long streams of characters rendering the email unreadable with the Subject and Sender not shown. The longest string is a heavily coded stream of characters interspersed with @btinternet.com, I assume this the encoded BCC list but only of the first 11 users in the list of 20.
Our members have been discarding them as spam because they contain no sender's name or subject and look like "gobbledegook"..
I have separated the 20 btinternet.com users out into a separate BCC group in an attempt to find a way around this by sending emails in plain-text only but no difference. If I only include two members as BCCs the message goes through correctly.
Please note, this is not recipients wishing to block these messages as phishing or spam, they want to see them. Something is stripping the Subject and Sender and listing vast amounts of HTML (I assume) code.
If I send the same email using the same email sending software to each btinternet.com member individually as a BCC there is no problem.
Please can someone tell me why this is happening.
