You receive the following error when sending emails:
554: Sender Denied
- GFI MailEssentials for Exchange/Simple Mail Transfer Protocol (SMTP)
- All supported environments
Settings on the recipient server are blocking the mail flow.
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.
Check each possible root cause and amend to avoid the error.