Case 1: Not Receiving

On rare occasions, you might not receive mail from some of your contacts. The sender receives a notice that your mail has bounced because the Sender IP address has been greylisted.

As part of our mail server spam protection, we use a Realtime Blackhole Lists service (RBL) to identify and block mail from suspected spammers. The Sender IP is checked against many DNS based email greylists.

In case the Sender IP is greylisted, our mail server will reject that email, and the message will not be delivered to you.

Example: mail@domain.com: 550 Sender IP (XX.XX.XX.XX) is greylisted at new.spam.dnsbl.sorbs.net

This issue is often confused with a problem upon receipt while it is entirely related to the sender’s IP reputation. Unfortunately, it is not possible to whitelist sender IPs. If you would like to accept email from such senders, you can disable blacklist protection per mailbox in your hosting control panel.

Case 2: Not Sending

In other occasions, when using our SMTP server, you might not be able to send emails, and the error looks like:

server response was: 550 Sender IP (XX.XX.XX.XX) is greylisted at new.spam.dnsbl.sorbs.net

This issue occurs because you are trying to use our SMTP without authentication, and your ISP IP is greylisted. The solution is to enable the “authentication when sending” function of your mail client.

• Outlook: enable the check-box “My server requires authentication”
• Eudora: enable the check-box “Authentication allowed”
• Mozilla: enable the option “Use name and password”
• Mail for Mac OS X: enable the check-box “Use authentication when sending”