I sent a email with addressee "123@yahoo.ca"
first email was sent ok. got an reply back from friend.
reply to his email..
failed delivery messages back...
look into the message....address was changed from from 123@yahoo.ca to 123@yahoo.com
thus it was undeliverable.
ok..used the email.. edited the address to correct one again 123@yahoo.ca
sent
fail delivery again.

I ended up using web yahoo mail to send. don't understanderd why 1st email sent ok..then failed twice.

anyone had similar problem?