I recently received a malicious email that was correctly entered as Spam, but the Government security web site suggests it was caused by historic security breaches and I strongly suspect the well documented Yahoo problems. I was dismayed when BT passed management of mail to Yahoo and I have tried to deal with this by using strong security processes, including the use of vpn. I am now finding it impossible to log in to BT mail without disconnecting vpn, which is very annoying and defeats the security. I don’t have problems with other email accounts that I have and I suspect the problem lies with Yahoo. If this can’t be resolved I won’t be using BT mail and won’t renew my expensive contract for internet etc.
BT is in the process of moving BTYahoo emails away from Yahoo and onto the BTMail platform.
Using a VPN would not/will not stop a similar hack that occurred at Yahoo. That was a hack at source ie the whole Yahoo servers database was compromised not just an individual users account.
If your email account was hacked in the 2014 Yahoo hack there is nothing you can do about it other than to stop using the compromised email account and even then if your contacts details were stolen at that time you can not "unsteal" them. They are permanently in the hands of the hackers and you can not stop the hackers spoofing your compromised email account.
see link about Spoofing.
If you are happy with the other aspects of your BT Broadband package, you do not need to move Internet Provider just to get an email account.
You are under no obligation to use BT as your email provider and in many ways you are best not to rely on an ISP based email account because it can prove problematic when/if you decide to move ISP.
Thank you for your very helpful and informative update. I did appreciate that VPN would not prevent the problem I experienced, but I’m not happy that I have to turn off my VPN just to receive my BT mail and so put my connection and computer at greater risk. I am pleased to hear that BT will be taking back control of their mail system, but they should never have moved it in the first place. I’m generally unhappy with the BT service, not least the high cost, and this is the final straw as it seems there is no answer to this problem till BT change their mail back. Thanks again.