E-mail address has changed?

[redbc]

I have been a BT Broadband customer for many years and during this time my e-mail address has been @btopenworld.com - it now seems to have changed, without me being informed, to @btinternet.com. This is now resulting in me getting messages saying that the organisation cannot respond to my e-mail as they do not have this new @btinternet.com address as my e-mail.  Can this be resolved ASAP and why has it changed - seems to have happened on e-mails I send since 16 June despite me always logging in with my @btopenworld.com address details

[licquorice]

They are one and the same thing and are interchangeable.

[redbc]

Yes, I am aware of that and have at times used the @btinternet format as my address but I use the @btopenworld.com as my main one. I am logging in as @btopenworld.com but it then logs me in as @btinternet.com and send emails from this address. This means that organisations do not recognise me and will not reply to my emails - how I can change it so that my emails still come from @btopenworld.com again?

[licquorice]

If you are using webmail, you can't as far as I'm aware. It was only possible on the BTYahoo mail system, not the new BTMail system.