SMTP Error Code : Server says: Server says: 503 This mail server requires authentication when attempting to send to a non-local e-mail address
Solution for Server says: 503 This mail server requires authentication when attempting to send to a non-local e-mail address
Here you will find instructions to add SMTP User Authentication details in GroupMail.
If you continue to have problems after adding or modifying the SMTP User Authentication details in GroupMail, contact the host of the Mail Server you are using to relay your email to explain the error and to confirm the details that you have entered.
As always, please feel free to contact the GroupMail support team. They will be happy to examine your settings for you.