Copied below is the text of a question from another user, which was never answered. I have the same problem every time I try to respond to or forward an email I have tried 3 times to get some help by messaging the BT email Help, their suggestions did not work.
" when I reply to some people I get the message 'Added by postmaster@btinternet.com' and pages of symbols/random letters are added making my message impossible to read as it is buried in the middle of the random additions. I phoned tech support but despite being put through to an email expert, it was clear he had no clue about anything"
Any suggestions of what to try next?