Troubleshooting 550 5.7.708 error from EXO

From time to time, when you start Office 365 trial with Exchange Online license, after some time you happen to be cut off from email communication and you get this NDR: Remote Server returned 550 5.7.708 Service unavailable. Access denied, traffic not accepted from this IP.

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Have you ever encountered the Outlook “something went wrong” error, after you switched on Multi-Factor Authentication in Office 365?

If you have seen the screen below, you should definitely continue reading, because I’m gonna share with you very simple solution.

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Using client_credentials with Microsoft Graph in Hybrid Exchange setup

If you or your customers are running hybrid Microsoft Exchange deployment and you are using Microsoft Graph, you might have noticed that using the client_credentials grant flow doesn’t really work and ends with errors. Last week, we have had a customer who we have been integrating few systems for, and hit the exactly same issue.

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SendGrid, forwarding and DMARC policy

We have recently deployed a strict DMARC policy (p=reject; sp=reject) on our domains. While this adds greater security while sending e-mail and prevents spoofing, we noticed that certain mails forwarded within our organization stopped coming in.

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Best practices for managing students in Active Directory

For quite a long time, we have been running a local service called SkolniLogin.cz which primarily focused on providing SSO experience for various systems at schools (primary and high schools) along with automatic synchronization with the school’s information system. Throughout the time we have hit a lot of edge scenarios, and compiled a best practices guideline.

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