I have ATT and can't send mail from my Mac Mail

I have ATT and for about two weeks, I am not able to send mail from my Mac Mail. I receive mail just fine. When I send out mail I get the following message. "Cannot send message using the server smtp.att.yahoo.com. The connection to ther server smtp.att.yahoo.com on port 995 timed out". And now the smtp shows (offline)

When I first got ATT I paid $50.00 for an ATT Tech to help me set up my Mac Mail, because I don't want to use the internet e-mail. When he talked me through the steps the first time, I made screen shots of every screen. I have checked all the entries and they are all the same. I have not changed anything. I have called and they want me to pay another $50.00. Does anyone have any suggestions? I have tried the new settings to inbound.att.net and the SMTP to outbound.att.net and 465 with SSL and this does not work either. Very frustrated. 😟