Question:

When I try to use the DNN newsletter module to send a newsletter, The following error message appears in the DNN event log for each e-mail address to which the newsletter is addressed.

AssemblyVersion: -1
PortalID: -1
PortalName:
UserID: -1
UserName:
ActiveTabID: -1
ActiveTabName:
RawURL:
AbsoluteURL:
AbsoluteURLReferrer:
UserAgent:
DefaultDataProvider:
ExceptionGUID:
InnerException: Mailbox unavailable. The server response was: No such user here

Resolution:

Our mail servers require SMTP-AUTH (smtp authentication) in order to send mail, and this error indicates you do not have these options set (i.e., you're trying to send the mail without first authenticating yourself as a valid mail user on the system).  To resolve, create yourself a mailbox/mail-user on your domain to be used for sending these newsletters (mailboxes can be created in the Control Panel using the MAIL icon).   Then update DNN's mail/newsletter options to enable smtp-authentication, and configure the mail-username and password you just created for sending these messages.  Be user to list the domain in the username... i.e., mynewsletter@mydomain.com.