I use yahoo webmail , there is one address , that I know is correct , that will not transmit from here , though I get these mails to my inbox no problem.To reply I send to my daughter in England and she forwards to EXACTLY the same address .Baffled or what ??

The address you are sending an email to might have your address marked as spam. What is your email address out of interest?
And I would recommend getting a gmail account.

I use yahoo , the recipient address is weird , @998.com turns out to be a company in Sheffield yet this person lives in Essex . I have suggested they get a Yahoo/gmail/hotmail address