The only reason for this to happen is that your SMTP server does not like either the SENDER or RECIPIENT of the message. Although most email servers
will accept any value for SENDER and RECIPIENT once authentication is used, some servers can be configured to apply more stringent rules.
For example, you can configure Microsoft Exchange to ensure that the SENDER of the message matches with the User ID used for authentication. Consider the
following scenario:
- User ID for SMTP Auth is
john.smith
- The actual sender of the email is
jane.doe@yourcompany.com
Since the public link is being created by Jane, her email address will appear in the FROM field and depending upon the configuration of your Exchange, it
may or may not reject this message. To check if this is the problem, try generating a public link using John's account and see if the message goes through.
To fix this, you must configure your SMTP server to accept messages from any sender as long as SMTP authentication is used.