This is why the ISPs throw up their hands at senders

I recently saw a question from an ESP rep asking if anyone had a personal contact at a particular ISP. The problem was that they had a rejection from the ISP saying: 571 5.7.1 too many recipients this session. The ESP was looking for someone at the ISP in order to ask what the problem was.
This is exactly the kind of behaviour that drives ISPs bonkers about senders. The ISP has sent a perfectly understandable rejection: “5.7.1: too many recipients this session.” And instead of spending some time and energy on the sender side troubleshooting, instead of spending some of their own money to work out what’s going on, they fall back on asking the ISPs to explain what they should do differently.
What, exactly, should you do differently? Stop sending so many recipients in a single session. This is not rocket science. The ISP tells you exactly what you need to do differently, and your first reaction is to attempt to mail postmaster@ the ISP and then, when that bounces, your next step is to look for a personal contact?
No. No. No.
Look, connections and addresses per connections is one of the absolute easiest things to troubleshoot. Fire up a shell, telnet to port 25 on the recipient server, and do a hand SMTP session, count the number of receipts. Sure, in some corporate situations it can be a PITA to do, sometimes you’re going to need to get it done from a particular IP which may be an interface on an appliance and doesn’t have telnet or whatever. But, y’know what? That Is Your Job.  If your company isn’t able to do it, well, please tell me so I can stop recommending that as an ESP. Companies have to be able to test and troubleshoot their own networks.
Senders have been begging ISPs for years “just tell us what you want and we’ll bother you less.” In this case the ISP was extremely clear about what they want: they want fewer recipients per connection. But the ESP delivery person is still looking for a contact so they can talk to the ISP to understand it better.
This is why the ISPs get so annoyed with senders. They’re tired of having to do the sender’s job.


  1. David Romerstein says

    But, y’know what? That Is Your Job.

  2. Suresh Ramasubramanian says


  3. Andrew Bonar says

    Fair point Laura. However AOL have also rejected a clients IP address recenlt from the whitelist. The reason given ‘Poor IP Reputation’. They follow best practices, generate no complaints, but still rejected and no indication of what has caused the ‘poor rep’.
    Will continue doing what they are doing and follow up in 30 days. Its frustrating though as they follow best practice and if there is a problem would love to know what it is. At the moment they arent providing enough infortmation to take it further. A generic link to best practice guidelines isnt very helpful in this instance.
    Had also signed up for the feedback loop with AOL, so will monitor this closely and see where it goes.

    1. laura says

      Andrew, I’ve written a lot about reputation, and reputation at AOL specifically.
      The short answer is: complaints are not the only thing AOL measures to determine a sender’s reputation.

  4. Maarten Oelering says

    Hear, hear, hear. I have seen even worse: senders not monitoring transient errors. They just keep on pushing their mails, often with software which is unfit for controlled delivery.
    On the other hand, there are many ISPs that send out messages which only a seasoned email guru can decode. For example, not many will know what a “550 Callout verification failed” means, or that a “554 Too many nonmail commands” could be caused by a sequence of unknown users.
    I would be great if all ISPs used enhanced status codes and clear messages like the one you described.

  5. Al says


  6. Karen Balle says

    Christine, who is unfortunately no longer with AOL, even blogged about permission vs request on the AOL postmaster blog.
    She went into great detail about what was ok and what wasn’t. Best practice means people who actually WANT the email and are interacting with the sender, not just low complaints. If the sender wasn’t already getting the FBL, how do you know that they had low complaints? They weren’t getting their complaints. If they’re being delivered into the spam folder, their complaints are artificially low. You can’t click the spam button on email that’s already in the spam folder.

  7. Annalivia says

    Following best practices does NOT guarantee the mail will get a good response from the recipients. Regarding the lack of specificity from ISPs, AOL in particular, see my post:

  8. The Proverbial Barry says

    if the words do not make sense to you then you should learn them or pay laura to teach you or go back to fliping burgers
    no i do not want fries with that spam

  9. Mohammed says

    I don’t know why everyone thinks that white listing IP address is like getting a free pass to sent. There are checks and balances to see how your IP/domain name is doing at the given time. You always have to take care of your mailing/complaints/honeypot/hard bounce backs and your mailing will go through fine without any problems.

  10. Brett says

    Seem to me that if ISP’s are going bonkers their is a problem.
    Any problem that involves massive repetition that impacts company resources should be fixed. Creating distance from this matter rather than service is a poor choice.
    ISP’s implementing better information will be the key.
    That is if they stop throwing their hands in the air so the can do some work.


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