This guide explains how RBLs work, the questionable policy of some of them, and the ways to resolve a potential email block.

Preamble

• RBLs (Realtime Blackhole List) or DNSBL (DNS Black List) are lists containing addresses / IP / provider names / servers, known as major spam senders.
• These are often large generalized blacklists, allowing to spot messages considered as unwanted and those who send them, that some providers maintain (smtpcheck, uceprotect: non-exhaustive list)…

Adding the email address to the RBL

When an email address is identified as belonging to an unwanted sender, it is blocked to prevent the reception of unsolicited messages. A block in the RBL does not expire. Addresses will be listed indefinitely.

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

Resolving an email block (RBL)…

… if the error mentions your address and RBL

If you get errors of the type

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

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

To avoid having your email address blocked by the RBL blocking system in the future, follow the best practices for using email:

1. Do not send unsolicited messages or mass messages to unknown recipients.
2. Regularly sort the list of recipients used.
3. Do not participate in phishing or cybercrime activities.
4. Ensure the best 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.)
   4. up-to-date associated domain configuration

... if the error mentions an organization like Sorbs or Barracuda

If you get errors of the type

554 5.7.1 Client host blocked using sorbs

or similar:

1. Follow the procedure of the mentioned organization (e.g. http://www.barracudacentral.org) to get your address removed from the list.
2. Temporarily change 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 the necessary steps and/or to stop using an unreliable RBL.
4. Wait a few hours and try again.

Fewer and fewer professionals (ISP, hosts, etc.) use service providers like Backscatterer / UCEPROTECT which are primarily for profit, and there are many other very effective lists, such as ABUSIX or SPAMCOP, which are well-maintained and whose real goal is to fight spam, one of the priorities of Infomaniak.