What is the outbound IP address used by my self-hosted n8n (Docker) when sending emails through the Outlook node, so I can whitelist it with Microsoft?

[krp]

Describe the problem/error/question

I am unable to send emails from a new business Outlook account using the Outlook node, receiving an IP-based rejection error from Microsoft. My older business account works perfectly in the same n8n workflow. Microsoft support states the sending IP address is blocked and needs whitelisting, but I don’t know how to identify which IP address my self-hosted n8n (Docker) is using to send these emails.

What is the error message (if any)?

The node execution shows as successful, but the email fails to deliver with this bounce message:

Remote server returned '550 5.7.708 Service unavailable. Access denied, traffic not accepted from this IP.
For more information please go to http://go.microsoft.com/fwlink/?LinkId=526653 AS(7230)
[SJ5PPF909964257.NAMP221.PROD.OUTLOOK.COM 2025-12-11T17:44:56.885Z 08DE3883C5938E6E]'

Please share your workflow

Share the output returned by the last node

[
{
“json”: {
“success”: true
}
}
]

Information on your n8n setup

• n8n version: 1.121.3
• Database (default: SQLite):
• n8n EXECUTIONS_PROCESS setting (default: own, main):
• Running n8n via (Docker, npm, n8n cloud, desktop app): Docker
• Operating system: Windows 11

[Nestor]

hi,
-open a terminal and do:

docker exec -it -u=“root” n8n /bin/sh

if n8n is the name of the container (you can check this with docker ps)
-then you do

ifconfig

and you will see your IP under eth0

[krp]

Hi,

Thank you for the guidance on using ifconfig. I ran the command in my n8n container and can see the network information.

Looking at the output for eth0, I see two different addresses listed: inet addr and Bcast.

To make sure I contact Microsoft support with the right information, could you please clarify—which one of these is the sending IP address I should provide to them for whitelisting?

Also, is this the only IP they need, or could there be other outbound addresses involved in sending the email that should be whitelisted too?

Thanks again for your help!

[Nestor]

inet addr should be the one, but i don’t know about what the outlook side need…

try and maybe i can help with the error message if it’s different

Ps; please reply to this message so i get notified

[krp]

Thanks, I’ll try this with Outlook team and get back to you.

PS: I’ll reply here if there’s a different error.

[krp]

Hey, just wanted to update you—sending the inet address to Microsoft for whitelisting worked! Everything’s working now, and I’m able to send emails through the automation without any IP issues. Thanks a lot for your help!

[Nestor]

good! I’m happy to hear this, please close the thread and mark the message with the solution for future reference.
Have a nice one