Hi @ all

Actually we have massive problems sending to private microsoft customers 
(hotmail.com, live.com, etc.)
We offer some small smtp mailservices for our customers (smtp smarthost and 
also a mail encryption and sign service).

The standard configuration of our outbound smtp servers is from my point of 
view set correctly:

  *   Fix IP
  *   Correct SMTP Banner, HELO, RDNS
  *   A Records matches RDNS
  *   SPF Records pass
  *   Tested DKIM signed

  *   Not on any Blacklist (checked with mxtoolbox.com)
  *   No spam activities on this /24 ip range for at least 6 years
  *   Sending to Microsoft Office 365 (Business Customers) works.

We registred our IPs on the Microsoft Smart Network Data Service (SNDS).
This only reports "All of your IPs have normal status".

The MS Support "does not see anything that would preventing your mail from 
reaching our customers". But it's MS servers that bounce the mail...

Remote Server returned '554 5.7.1 <hotmail-com.olc.protection.outlook.com 
#5.7.1 smtp; 550 5.7.1 Unfortunately, messages from [xx] weren't sent. Please 
contact your Internet service provider since part of their network is on our 
block list (S3150). You can also refer your provider to 

Has anyone experince with this sort of problem?

thanks and great day.


Freundliche Grüsse

Marco Kälin

+41 79 177 11 76 | marco@kaelin.email

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