Best Practices Why Did AOL Send Me “554 (RTR:BL) http://postmaster.info.aol.com/errors/554rtrbl.html”? By Ken Simpson | 3 minute read In this latest post of a series of blog posts where we attempt to demystify the most common SMTP error codes, today we discuss AOL’s very common 554 error code: 554 (RTR:BL) http://postmaster.info.aol.com/errors/554rtrbl.html What does AOL’s v 554 error code mean? If you received this error message in your inbox, it means that you tried to send someone at AOL an email message, and AOL rejected the connection from your mail server because your mail server’s IP address has sent a great deal objectionable content such as spam to AOL. AOL states the cause on its Postmaster web site as follows: This error message indicates that a permanent block has been placed against your IP due to poor IP reputation. Apply for a complaint feedback loop before opening a support request. What can I do? This error message indicates that AOL’s email systems have taken an extreme disliking to your mail server’s IP address. To get this far, you need to send AOL a large amount of spam and other objectionable material about which AOL users have complained. This is a “permanent” block, which means it’s going to take some time and serious effort to resolve the problem. Solution: Locate accounts that are sending spam via your mail server’s IP address, and shut them down. You probably have more than one of these. What else can I try? Carefully review AOL’s Postmaster pages and follow their recommended best practices. Sign up for a feedback loop, which is a mechanism that allows AOL to report user complaints directly to you so that you know what types of email AOL users object to. Install outbound spam filtering, track your users’ behaviour, and shut down abusive accounts in your own network. Temporary Measures As a very temporary measure, if you can send through a different mail server, that might help to get your email delivered more reliably. For example, if you have a Gmail account, use the Gmail SMTP server to send your mail. Its host name is smtp.gmail.com. You’ll need to enable TLS security, and provide your username and password in order to use Gmail’s SMTP server. More information can be found on the Google Support Site. Obtaining a new IP address for your mail server may be another way of solving the problem; however, if you do this frequently, be advised that AOL will eventually figure out your game and will beging blocking larger parts of the address space from which you send. Bottom Line Fundamentally, if you see “554 (RTR:BL)”, it’s time to get serious about filtering your outbound email traffic, identifying sources of abuse such as compromised accounts, and generally improving the quality of the email you send so that AOL users don’t complain about it.