Resolve an email block (RBL)

This guide explains how RBLs work, the contentious policies of some of them, and how to resolve a possible email block.

What is RBL?

RBLs (Realtime Blackhole Lists) or DNSBLs (DNS Black Lists) are lists containing addresses / IPs / provider names / servers, known as major spam senders.

They are often large generalized blacklists maintained by certain providers (smtpcheck, uceprotect: non-exhaustive list)...

When an email address is identified as belonging to an undesirable sender, it is blocked to prevent receiving unsolicited emails. An RBL block does not expire. Addresses will be listed indefinitely.

What to do in case of a block?

If you receive a message indicating that your email address is blocked by RBL, it means that the Infomaniak security system has detected suspicious or undesirable activities associated with this email address. This may include bulk sending of unsolicited emails, participation in phishing campaigns, or other malicious behaviors.

If the error mentions your address and RBL

If you receive errors like

anna.a@domain.xyz is rbl blacklisted - http://chk.me/rbl

when sending an email and you think it is a false positive, contact Infomaniak support.

To avoid having your email address blocked by our RBL blocking system in the future, follow good email usage practices:

1. do not send unsolicited emails or mass messages to unknown recipients (learn more)
2. regularly clean your recipient list
3. do not participate in phishing or cybercriminal activities
4. ensure the highest level of security where your emails are used:
   1. strong password
   2. up-to-date software
   3. up-to-date operating system (iOS, Android, Windows, macOS, etc.)

If the error mentions an organization like Sorbs or Barracuda

If you receive errors like

554 5.7.1 Client host blocked using sorbs

or similar, you should:

1. follow the procedure of the mentioned organization (e.g., http://www.barracudacentral.org) to request removal of your address from the list
2. temporarily switch your Internet service provider or connection method - WIFI vs 4G/5G - to send your messages
3. inform your correspondent and their email provider to take necessary actions and/or not use unreliable RBLs
4. wait a few hours and try again

Fewer and fewer professionals (ISPs, hosting providers, etc.) use providers like Backscatterer / UCEPROTECT, which are primarily financial in nature, and there are many other very effective lists, such as ABUSIX or SPAMCOP, well maintained and with the real goal of fighting spam, one of Infomaniak's priorities.