Does yahoo have an online tech support chat?

My yahoo email acct, that I had many years, suddenly got a problem. I cant send, reply, or forward anything, with a new address, or from my contact list, which has not changed for years. I get an error message, "MESSAGE COULD NOT BE SENT FOR THE FOLLOWING REASON MISSING OR MALFORMED FROM ADDRESS" I... show more My yahoo email acct, that I had many years, suddenly got a problem. I cant send, reply, or forward anything, with a new address, or from my contact list, which has not changed for years. I get an error message, "MESSAGE COULD NOT BE SENT FOR THE FOLLOWING REASON
MISSING OR MALFORMED FROM ADDRESS"
I have tried all the suggestions from yahoo help. Cleared cache, changed browsers, etc. My other yahoo acct works fine with the same contacts.
What is going on???
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