Hi Marco

Same here, randomly refused with exactly same situation, no data on SNDS and MS support says the same

Cheers Salvatore

________________________________ From: swinog-bounces@lists.swinog.ch swinog-bounces@lists.swinog.ch on behalf of Marco Kälin marco@kaelin.email Sent: Tuesday, November 16, 2021 9:14:02 AM To: swinog@lists.swinog.ch Subject: [swinog] Problem sending to hotmail / block list S3150

This is the first time you've received an email from this sender. Make sure this is someone you trust. 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 http://mail.live.com/mail/troubleshooting.aspx#errors. [DM6NAM04FT044.eop-NAM04.prod.protection.outlook.com]

Has anyone experince with this sort of problem?

thanks and great day.

Marco

Freundliche Grüsse

Marco Kälin

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

On 20211116, at 09:14, Marco Kälin marco@kaelin.email wrote:

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

You mean EHLO right? :)

• A Records matches RDNS

Thus the FCrDNS check works?

As it is 2021... you do have an AAAA record and are capable of sending over IPv6 I hope?

• SPF Records pass

What is the policy, maybe ~all at the end? Maybe "ip4:0.0.0.0/24 -all"?

• Tested DKIM signed

Don't forget about DMARC, otherwise SPF and DKIM are pretty meaningless

And if you are forwarding messages, ensure to rewrite the From appropriately otherwise you break all kinds of things.

Not on any Blacklist (checked with mxtoolbox.com)

But is your network neighborhood clean. As you didn't provide any IPs, cannot verify that is the case.

If you host for instance at OVH or other such institutions except the /20 that your IP is in to be considered a bad neighborhood; and thus while your host is 'nice' the rest is not...

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

For low volume senders SNDS does nothing as you just don't send enough mail to get into their stats (see for instance https://jeroen.massar.ch/presentations/files/FloCon2010-TopK.pdf).

These facilities are setup for big spammers so that they can send 100.000 mails and can have 1% spam amongst them (still a 1000 mails of spam, see why those end up in your mailboxes...)

The more and more that services on the Internet get centralized the more this will happen unfortunately.

As you are a Microsoft customer for kaelin.email according to the MX, use that contract to call them and tell that you cannot send mail from your IP.

Without actual full headers, little else people on a public list can say but: contact them through a paid contract.

Though they will likely point you to https://sendersupport.olc.protection.outlook.com/pm/policies.aspx or https://sendersupport.olc.protection.outlook.com/pm/services.aspx.

Don't forget to signup for the "Junk Email Reporting Program" @ https://postmaster.live.com/snds/JMRP.aspx though, as noted, you can be sqeaky clean, if others in a similar related subnet are not....

Or your volume can just be way too low.

Greets, Jeroen