Every once in a while we find something humorous about the gory details of email delivery and just have to share it. In today’s episode, we have an ISP that called out an ESP as “accepting spammers as clients” within their bounce codes. Read on!
What’s a bounce code?
We’re parsing through millions upon millions of response codes from ISPs like Gmail, Yahoo!, and thousands of others. Every time you send an email, there’s a response of some kind from that mailbox provider. When all is good, you might see something like this:
250 2.1.5 OK
As you can see, this response simply includes a couple of numeric codes (of which there are many), and a message describing things in more detail. In this case, just “OK”.
When all is not so good, you might see:
554 5.7.1 Message Rejected
Hopefully there’s more detail than this, but it’s not always the case. Each of these messages can be customized by the mailbox provider or ISP and every once in a while we find a gem that deserves sharing!
Ok, give me the funny one!
This week, we saw one that made us laugh. In this case a mailbox provider was specifically calling out an ESP as being a spammer haven! We’ve redacted identifying information to protect the innocent, and not-so-innocent.
554 5.7.1 <email@example.com>: Sender address rejected: mail from “sender-domain.com”. “esp-domain.com” is blocked for spamming spamtraps .. stop accepting spammers as clients
Have you seen any funny ISP response codes? We’d love to hear about them in the comments…