My mom is having an intermittent problem sending mail from Mac Mail (incoming mail is fine). It will work for a while, then stop working, with this error: Cannot send message using the server SMTP. Verify that you have addressed this message correctly. Check your SMTP server settings in mail preferences, and verify any advanced settings with your system administrator. SMTP AUTH is required for message submission on port 587 Select a different outgoing mail server from the list below or click Try Later to leave the message in your outbox until it can be sent. I found some information on GreenNet about a known issue with Mac Mail on Yosemite, so will log into her machine remotely and reset her email password, etc. Have you seen this? Is there a permanent solution?