You receive the following error when sending mail:
554: Sender Denied
- GFI MailEssentials for Exchange/SMTP
- All Supported Environments
This will normally appear when the recipient has blocked the email in some way. Reasons for this could be:
- Email sent From: an invalid domain name.
- The email address is blocked.
- The entire domain portion of the email address is blocked.
- The IP address is blocked.
- The IP address is listed in a blacklist.
Settings on the recipient server are blocking the mail flow.