Outlook.com is no longer blocking my mail server

I’ve been getting quite a few emails from people wanting to know if I’ve made any progress on the deliverability issues I was facing when delivering email to outlook.com. As good fortune would have it, Microsoft accepted my request to delist my mail server from outlook.com’s internal IP blocklist.

This is a follow up to my “Outlook.com is blocking my mail server” article, so please refer to that for additional context.

Getting de-listed from outlook.com’s blocklist

There are no guarantees that your mail server will be unblocked, but you’ll at least be able to request a manual review if it’s determined that your IP(s) don’t qualify for mitigation.

Prerequisites

Before requesting a manual review, I would suggest checking the configuration of your mail server. There are multiple online services available for that purpose. I’ve mentioned a couple in a previous article I wrote about self-hosting email.

I would also recommend to sign up for the Smart Network Data Services and JMR programs freely offered by Microsoft.

Additionally, and it goes without saying, but do make sure to comply with Microsoft’s policies, practices, and guidelines.

Arguing my case

I’ll just post the relevant extracts from the communication I had with Microsoft to give an idea of how the process works. I’m not sure if “arguing” my case had any influence on the result as every reply from Microsoft appeared to originate from a standard response template.

Anyhow, what mattered, in the end, was to have a couple of human eyes looking into the actual traffic originating from my mail server.

My request for a manual review

Hello!

I would like to ask to have 159.89.83.93/32 (server3.paranoidpenguin.net) considered manually delisted from the outlook.com blocklist.

According to the IP status page with Smart Network Data Services (SNDS), my mail server with the IP address of 159.89.83.93/32 is blocked due to user complaints or other evidence of spamming.

I do believe, however, that 159.89.83.93/32 is simply being blocked as a consequence of a larger sweep against my service provider DigitalOcean.

The mail server adheres to all Microsoft Policies when delivering email to outlook.com. I actively monitor 159.89.83.93/32 with Smart Network Data Services (SNDS) and Junk Email Reporting Program (JMRP). I have never received reports that any outlook.com user has marked my email as spam.

The following technologies are implemented on my mail server for authentication and secure communication:

• SPF, DKIM, and DMARC.
• StartTLS and DANE
• MTA-STS and TLS-RP

Additionally, I can offer the following:

• The mail server 159.89.83.93/32 is not listed on any public blocklist.
• The mail server 159.89.83.93/32 can deliver email to every other major service provider, including Office 365 tenants.
• The mail server 159.89.83.93/32 is for personal use only and doesn’t send unsolicited emails.

I’m happy to address any concerns that the outlook.com deliverability support team might have.

Smugly basking in my own glory, I eagerly awaited a response from Microsoft. Somewhat surprising, I got the first reply within an hour.

Microsoft reply #1

Hello,

My name is <redacted> and I work with the Outlook.com Deliverability Support Team. We will be looking into this issue along with the Escalations Team. We understand the urgency of this issue and will provide an update as soon as this is available. Rest assured that this ticket is being tracked and we will get back to you as soon as we have more information to offer.

Thank you for your patience.

A day later, I received the second reply containing the final verdict.

Microsoft reply #2

Hello,

Recent activity coming from your IP (159.89.83.93) has been flagged by our system as suspicious, causing your IP to become blocked.

I have conducted an investigation into the emails originating from your IP space and have implemented mitigation for your deliverability problem. This process may take 24 - 48 hours to replicate completely throughout our system.

As promised, the block was removed and I could once more deliver email to outlook.com recipients.

I have no idea if my mail server will prevail when the ban hammer falls on DigitalOcean again, but for now, I count this as a small win for decentralized email.

Pay it forward

In related news, messages from my mail server are no longer automatically flagged as junk upon delivery to outlook.com. I find that to be a most peculiar and happy coincidence.