outlook 365 server problem

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outlook 365 server problem

Sven Alder 0

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hello, over the last 2 weeks I have been having this issue when sending emails. I have looked everywhere to find a solution and nothing has worked. I then installed EM Client and have not had a single issue with this software. Can anyone offer any type of solution.

Hornblower409 7,645 Reputation points

2026-03-24T05:06:12.4233333+00:00

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Hornblower409 7,645 Reputation points

2026-03-24T05:06:12.4233333+00:00

If the Q&A Assist Answer did not solve your problem:

Click the [No] button on the "Was this answer helpful?" bar under the answer. If there is a [Reject] button visible, click that too. This should signal the forum moderators that you want a human to pick up this question.

If that does not get you a human response, type "Not Solved" in the "Add Comment" box below and then click the [Add Comment] button. I will try to offer some suggestions on what you can do next.

Answer 1

The warning indicates that the mail server Outlook connects to is presenting an SSL/TLS certificate chain that Windows does not trust. EM Client working while Outlook does not suggests a configuration or trust issue specific to Outlook/Windows rather than the server being completely unreachable.

Because the context only covers generic Outlook send/receive issues and not certificate‑trust configuration, the only supported steps are the general Outlook connectivity and repair actions:

Make sure Windows and Office/Outlook are fully updated.
- Run Windows Update to install the latest updates for Windows and Microsoft 365 apps.
Run the Outlook/Connectivity troubleshooters for classic Outlook.
- Go to the Classic Outlook troubleshooters page and run the appropriate troubleshooter for send/receive issues.
If multiple users in the same tenant see similar issues, an admin should:
- Check Microsoft 365 Service health for Exchange Online to rule out service‑side issues.
If problems persist after using the troubleshooters, contact Microsoft Support for deeper investigation of the certificate trust and profile configuration.

If the issue is only with a specific account or profile, support may recommend recreating the Outlook profile or adjusting account settings, but those steps are not detailed in the provided material.

References:

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