Forum Discussion

omdel's avatar
omdel
Tuning in
2 months ago

Issues with email delays and bounces, postmaster not responding

Hi, we have seen a number of senders/IPs be affected with emails being delayed and then bounced due to '421 4.1.1 MXIN503 Hourly ratelimit for your IP exceeded '.

In all cases the email volumes are not that high, and in fact lower than say over the Black Friday and Christmas periods where we saw no rate limiting.  I contacted the postmaster@virginmedia.com postmaster address on one instance 10 days ago and have had no reply at all. Is this no longer the correct contact address for the postmaster team?

I now have another case to report for a shared IP pool where max volumes per IP is around 6k mail an hour which really is not high at all, yet as far s we can tell we see this rate limiting happen if there is more than 2k an hour being sent. 

 

 

5 Replies

Sort By
  • Kath_P's avatar
    Kath_P
    Icon for Forum Team rankForum Team
    2 months ago

    Hi omdel, 

    Thanks for taking the time to contact us via the Community. It's lovely having you on board with us in the Forums. ⭐

    We're sorry to hear you're having issues with sending emails. 

    The error you've posted means that you've made too many requests from your current IP address within a one-hour period, causing the server to temporarily block further requests from your location due to its rate limiting policy. 

    Just to give you a breakdown of the code:

    • ➡ 421: This is the SMTP (Simple Mail Transfer Protocol) response code indicating a temporary failure, meaning you should try again later.
    • ➡ 4.1.1: This is a more specific error code related to a "sender rate limit exceeded" situation.
    • ➡ MXIN503: This is the server's specific identifier for this type of error, likely indicating a "maximum incoming connections" limit has been reached. 

    The simplest solution is to wait for a short period (usually an hour) before attempting to send emails again from the same IP address. If you are sending a large volume of emails quickly, consider spreading them out over a longer time frame to avoid exceeding the rate limit. 

    As you've already contacted the postmaster email address, the teams there will look into this and come back to you directly with a reply. 

    Many thanks, 

    • omdel's avatar
      omdel
      Tuning in
      2 months ago

      Hi, thanks for your reply, however we have already tried your suggestions and the issue is still ongoing in most cases. We have retries built into out system and even when these get down to only having a few hundred left to deliver and nothing else is sending to Virgin they are still being delayed and in many cases delayed so long that the emails time out.

      Spreading the volume out also leads to very little improvement and some of our clients have received angry messages from Virgin contacts who have missed otu on offers as a result of these issues. As mentioned we have previously had these same senders sending much higher volumes in shorter time frames without any issues and it is unclear what has now changed.

      Also waiting 12 days to hear back from a Postmaster on this is very frustrating.

      • Carley_S's avatar
        Carley_S
        Icon for Forum Team rankForum Team
        2 months ago

        Thank you for this omdel.

        We'd need to be able to see the data on these emails failing from the end user, such as headers and data that we can use to raise this issue further. 

        How do you send your emails? is this through our webmail or through a web client like Gmail or Outlook? 

         

    • ravenstar68's avatar
      ravenstar68
      Very Insightful Person
      2 months ago

      Kath_P 

      Everything in the OP screams that this is an email admin posting here, the fact that they've had no response from the postmaster should be troubling.

      For reference ALL normal email servers see errors in the 4xx range as temporary errors, thus they will automatically retry the mail send at intervals until either the mail gets through or until the server retry timeout is exceeding. So the OP shouldn't be advised to try again.  This is part of the email standard.

      In my opinion, ironically rate limiting like this can, if done incorrectly, INCREASE the amount of connection attempts made from the blocked IP, thus leading to more failures.

      Carley_S 

      My advice to you is to read the OP carefully, this isn't a Virgin Media customer, this is an email admin who's having issues delivering TO Virgin Media customers and is coming to the Forum as they are getting no response from the Virgin Media Postmaster address.

      Yours

      Ravenstar68

  • omdel's avatar
    omdel
    Tuning in
    2 months ago

    Thank you @Ravenstar68 you are correct.

    @Carley_S We are a commercial ESP whose clients are commercial brands sending to Virgin customers. 

    We can provide header details however we can only provide redacted ones which wouldn't be of use in this scenario due to our security policies - due to the rise in spammers stealing and re-using header details from legitimate emails we will not be exposing our infrastructure or client domains publicly. 

    This is why we have been trying to contact the Postmaster through their address as we can provide those details to them there. However we still haven't even had an acknowledgement from them at all. If you can provide a private channel for supplying these details we would be happy to.