Can't send mail to Microsoft accounts.

Is the Linode address space on a black list somewhere?

My Linode host is configured as a mail server with iRedMail. I am blocked sending to Microsoft accounts (i.e. Hotmail, Outlook).

For Hotmail I get the following:

Jan 27 12:47:09 mail postfix/smtp[4553]: 22C671E47D: to=<[email protected]>,[]:25], delay=0.44, delays=0.01/0.03/0.37/0.04, dsn=5.0.0, status=bounced (host[] said: 550 SC-001 (SNT004-MC2F7) Unfortunately, messages from weren't sent. Please contact your Internet service provider since part of their network is on our block list. You can also refer your provider to (in reply to MAIL FROM command)),</[email protected]> 

The error they reference: 550 SC-001, states:

"Mail rejected by for policy reasons. Reasons for rejection may be related to content with spam-like characteristics or IP/domain reputation. If you are not an email/network admin please contact your Email/Internet Service Provider for help"

The mail is not "spam-like" so it must be the reputation of the IP/domain.

For Outlook I get:

Jan 27 12:47:51 mail postfix/smtp[4553]: D81AF1E47D: to=<[email protected]>,[]:25], delay=6.3, delays=0.01/0/0.62/5.6, dsn=5.7.1, status=bounced (host[] said: 550 5.7.1 Service unavailable; Client host [] blocked using FBLW15; To request removal from this list please forward this message to [email protected] (in reply to RCPT TO command))</[email protected]> 

I've requested delisting but have heard nothing back.

Any ideas?

8 Replies

Please refer to the thread below for learning about mail ejection by Microsoft Outlook - … ed9a0?db=5">

Also, check your ip and see if any of your neighbors have a bad reputation.

I belive Linode may be allowing bad players to pollute the email reputation of a block of ip's. (don't know for sure). Have asked support about this and nothing so far.

Yes. Linode is on UCEPROTECT Level 3 blacklist (ASN 63949) due to an extremely high spam score for the ASN. Not sure if this means all Linode IP's or not, but certainly mine is on the block list, simply because some of my neighbors have been naughty.

My specific IP, and the subnet it is on, come up clean on every blacklist I have checked, and I have all the currently proper authentication and verification measures successfully in-place and passing (i.e. DKIM, SPF, DMARC, PTR, MX and so forth).

I have tickets open with both Microsoft and Linode, however have not heard anything as of yet.

Apparently, since my rep is clean (not on Level 1), I am allowed to pay (who runs UCEPROTECT) to have my IP specifically removed from the blacklist for the equivalent of about $30 per month or $60 for six months, etc.-- although it is unclear as to whether this will alleviate the block from's servers.

Personally, I feel this is extortion, as I have done nothing wrong and my server has never been compromised, nor sent out spam or even mailing lists of any sort.

All I did was everything right, except had some shady folks move into the neighborhood.

I understand they need to make money too, but none of this was my fault, nor my choice. Just a victim of circumstance, like yourself.

Hopefully this will be resolved soon.

Hi. Thanks. Went through the process of manually de-listing with for individual IP block as recommended in the first set of bounces, then contacted Linode Support as recommended in the bounces afterward. Tested send/receive OK with address, no more bounces.

Note: I had all the recommended security checks successfully in-place before-hand, namely SPF, DKIM, DMARC, and PTR. If you don't have these, you will want to implement them first. Also, be sure to clear up any other black-list issues, if you can. This was part of the reason MS was so quick to unblock me, since I've had all those checks in-place and have had a clean record regarding both my server and it's IP.

@jdmayfield writes:

This was part of the reason MS was so quick to unblock me, since I've had all those checks in-place and have had a clean record regarding both my server and it's IP.

I would say that you got very, very lucky. M$ could have just ignored you or told you to take a hike. IMHO, those two outcomes are much more frequent than the one you received.

-- sw

Hi, stevewi.

Not just luck. MS doesn't want to block legitimate senders. That's bad for business. What I did was fulfill all of the requirements, had no history of spamming, a fairly long history with my server's IP (~5 years), and followed their requested processes, which included reaching out for help from my ISP (Linode). This last step was specified clearly in the bounce messages.

Probably doesn't hurt that I've helped Outlook a couple of times with their own deliverability issues (i.e. mismatched DKIM keys I discovered a few years ago, causing their mail to be rejected or quarantined by servers world-wide).

Yes, they could ignore me. But this isn't my first rodeo. I do this kind of thing at my day-job all the time. I'm a Network Administrator for a small-town ISP and computer shop. I personally handle the mail-servers at work as well, and have dealt with this issue before.

Sometimes the squeaky wheel really does get the grease.

"Not just luck. MS doesn't want to block legitimate senders. That's bad for business."

Well they are blocking us without any explanation. Pure extortion.
SPF, DKIM, DMARC all set. We're not blocked anywhere. Still we can't deliver email to our core business partners since they are using "*".

Very professional.
We will probably move away from linode to a custom dedicated email provider. We're losing flexibility and good service but we're forced to do it.


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