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503 rate limiting - who to contact?

Hi there,

We have an issue with emails to our members with ntlworld, blueyonder and virgin email accounts getting blocked in much the same way as a community member previously replied to in August as below.  I was hoping we could find some way of ensuring that our emails get through as they contain information that is important to them as members of a Trade Union  

'Re: 503 rate limiting - who to contact?

The bounces occur anytime mail is sent to a recipient at,,, or any other Virgin Media domain. This would seem to indicate Virgin Media is the one throttling the mail. Here is the format of the SMTP responses:

421 4.1.1 logid=SMTPRC 421 MXIN503 Hourly ratelimit for your IP exceeded ;id=AWVhjLA2wxWCGAWVijB69A;sid=AWVhjLA2wxWCG;mta=mx11.tb;d=20200307;t=111646[CET];ipsrc=xx.xx.xx.xx





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Re: 503 rate limiting - who to contact?

You would normally go the Postmaster for VM to discuss this directly and you would know the standard format for the Postmaster's e-mail address. I can't quote it here.

VM rate limit because they think your mail is or looks spammy. That strongly implies that you are either sending too many emails per hour (as in the error message) to your members.  More likely the DMARC. DKIM, and SPF checks that VM are increasingly applying to its incoming mail are giving cause for concern.  It could even be that your mail server is misconfigured so that the DNS lookup and reverse DNS look up point to the wrong place or don't point to a FQDN. VM are strict here. If the formal of you mail isn't precisely correct what you see happening is what is designed to happen.

I think we'd best leave this now to the VM Forum Team here who can discuss with you the best way forward. They may include direct discussions with the Postmaster or asking you to provide more information so the matter can be investigated. 

Watch this thread for a reply in the next few days.


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