outlook-com.olc.protection.outlook.com incomplete/not precise message, needs more details


Today while trying to send a email from my email server to a @hotmail account I got: (my IP suppressed in the following copy)

    "outlook-com.olc.protection.outlook.com[] said: 550 5.7.1
    Unfortunately, messages from [*.*.*.*] weren't sent. Please contact
    your Internet service provider since part of their network is on our block
    list (S3140). You can also refer your provider to
    [SN1NAM01FT015.eop-nam01.prod.protection.outlook.com] (in reply to MAIL
    FROM command)"

Accordingly the guidelines "https://sendersupport.olc.protection.outlook.com/pm/troubleshooting.aspx" there are 8 different cases for '550' code, from 550 SC-001 to 550 OU-002 but the message returned to my host doesn't specify which was the case among the 8. it looks like a important piece of information to get started troubleshooting.

1- Anyway, most importantly: The message says that "... part of their network is on our block list ...". It means that outlook host is really blocking entire subnets? As example in the /24 sub my IP is located just 2 IP's have a poor email reputation, one of them is blacklisted, and it's not my IP. (Scanned with https://www.talosintelligence.com/reputation_center)

2- And finally: Have been using my IP for years now without problems, sending low-traffic e-mails for just one domain. Checked my logs and had just one email sent to outlook destinations (@hotmail.com, @live.com, etc) in the last 7 days, and it's this one that was blocked. If it's true that outlook blocks entire IP ranges there's a way to have my specific IP in a whitelist?

Appreciate any clue.



Hi Rodrigo,

A possible reason for this issue is that your IP address could be blocked by the Outlook server due to sending multiple emails and it was recognized as spam. A way to solve this is to fill up the IP delisting form so that the block on your IP address will be lifted. Please take note that you need to give some time for this issue to be processed due to the high volume of concerns that they are handling.  Click here if you want to fill-up the IP delisting form.

Let us know if you have other concerns.


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Last updated July 28, 2020 Views 707 Applies to: