Hello Email Marketers! :)

I'm new here, and looking forward to joining in discussion.

We've got a problem, and it's starting to put a grind on customer support.

About 4 days we started getting "rate limited" by microsoft/outlook/hotmail with this message:

SMTP service unavailable: "421 RP-001 (SNT004-MC1F19) Unfortunately, some messages from weren't sent. Please try again. We have limits for how many messages can be sent per hour and per day. You can also refer to http://mail.live.com/mail/troubleshooting.aspx#errors." received from hotmail-com.olc.protection.outlook.com ( while connected from outmail.myemailsend.com ( to hotmail-com.olc.protection.outlook.com (

We've been running our own email server and MTA for several years.

We send an average of 60,000 emails per day across 2 decent sized small businesses.

All confirmed opt in, permission based email. Some of it transactional in nature to our paid customers. We have stellar sender scores across the board (97's across all 4 of our IP's).

We've set our MTA to "pause" email sending to hotmail/outlook/microsoft email addresses for 5 minutes each time we get this message. The problem is, it's only letting a very few emails through before it sends this message and we pause the queue.

Now matter how many times I contact the outlook postmaster, I get the same autoresponse/mitigation of IP block emails...but I never get to communicate with an actual human.

Here's the postmaster support which I am using:


I've done this 2 times, and still the problem is not resolved and I get canned responses that the IP block is "mitigated", but nothing ever changes.

Does anybody know of any tricks to contact an actual human being to look into this issue? What options do I have?

Thanks for any advice you can offer. I appreciate it!