Zoho Recruit mailserver get blocked by Microsoft!

Zoho Recruit mailserver get blocked by Microsoft!

Hi,

We have experienced this issue twice now, where Zoho Recruit outbound IP addresses are being blocked by Microsoft. We are confident that Microsoft is the blocking party, as all outbound emails to candidates with @hotmail.com, @live.com, and @outlook.com domains are rejected.

In the most recent case, the IP address 136.143.168.39 was blocked. Previously, 136.143.168.119 was blocked. Both IP addresses are owned and used by Zoho Corp.

Is there any recommended solution to prevent this from happening, other than setting up an SMTP relay via our own server?


The message that we getting is this:
Your message to the following recipient was not delivered. Please find the details below.
Bounce Details:
Bounce email[user]@outlook.com
Bounce reasonuncategorized-bounce
Diagnostic Message5.7.1 Unfortunately messages from [136.143.168.39] 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. [Name=Protocol Filter Agent][AGT=PFA][MxId=11BD14F84FAE630D] [DB1PEPF000509F7.eurprd02.prod.outlook.com 2026-03-30T12:24:16.462Z 08DE8A7C2DE11711] Remote-MTA: dns; outlook-com.olc.protection.outlook.com
Bounce time03/30/2026 02:24 PM
Note: Above Candidate/Contact is marked as Opted-Out. Emails to the person will not be sent hereafter.

Regards,

Zoho Recruit Team