Mac 10.14.4 with apple mail 12.4 and user can no longer send e-mail with DMARC failure response. Client has Yahoo, Gmail, Centurytel, and iCloud e-mail accounts. No account can send e-mail due to every account was trying to use GMAIL for SMTP. Tried adding a iCloud SMTP server as Apple recommended, but once I select iCloud for SMTP on any account it quickly defaults back to None. I have scanned to computer for viruses with Avast Free, as the computer had no protection and she had fallen victim to a tech support scam on this computer.