can not get to server

Hi @Info - Marc Oliver Bathrooms, Kitchens & Tiles

To help us investigate and resolve this issue more effectively, could you please provide clarification on the following:

Is the affected mailbox hosted on Exchange Online, Exchange On‑Premises, or another email hosting service?

Is this issue impacting specific user, multiple users, or all users?

What is the exact error message you are seeing when attempting to access email?

Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to find a solution. 

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For an Exchange or other email server that suddenly cannot be reached, use these steps to narrow down and restore service:

1. Check if the mail server is online
   If email was working before and now no one can connect, the mail server may be offline or unreachable. Contact the email provider or network administrator and confirm the server status and any ongoing maintenance or outages.
2. Check network, firewall, and proxy
   • Verify that Internet access is working from affected machines.
   • If using a corporate network, confirm that no new firewall rules are blocking SMTP/IMAP/POP/HTTPS to the mail server.
   • If the network requires a proxy to reach external services, ensure the proxy settings are correct on client machines. A missing or incorrect proxy can prevent Outlook or other clients from reaching the mail server.
3. Verify client account settings
   On each mail client (for example Outlook or Outlook for Mac):
   • Confirm the correct email address, username, and password are configured.
   • Confirm the correct incoming (IMAP/POP) and outgoing (SMTP) server names and ports.
   • If the provider requires SSL/TLS or non‑default ports, ensure those are set exactly as required.
     If anything is unclear, check with the email service provider for the exact configuration details.
4. Check for TLS / protocol issues (IMAP/POP/SMTP)
   If Outlook or another client shows errors like “The connection to the server was interrupted” or “Your server unexpectedly terminated the connection,” there may be a TLS or app‑password issue:
   • If the account uses an app password (for example, with IMAP/POP), sign in to the provider’s webmail portal, go to the security settings, and generate a new app password. Update that password in the mail client’s account settings and test again.
   • On Windows 10 clients using Outlook with IMAP/POP, TLS 1.3 can cause connection failures. Removing TLS 1.3 from the Windows SCHANNEL Protocols registry key (as documented) and then restarting Outlook/Windows can restore connectivity. This change should be performed by an administrator because it modifies system security settings.
5. If only some addresses are affected
   If mail works generally but one address is not receiving messages, check for:
   • Misconfigured or hidden rules diverting mail (for example, to RSS or another folder).
   • Any temporary or alternate mailbox configuration that might be intercepting mail.
     Removing problematic rules or recreating the Outlook profile against the correct Exchange mailbox can restore normal delivery.

If these checks do not restore service, collect the exact error messages from clients and server logs (SMTP/IMAP/POP/TLS errors) and provide them to the email provider or Exchange administrator for deeper diagnosis.

References:

• Outlook IMAP or POP server unexpectedly terminated the connection, and the server was interrupted
• I can't send or receive messages with Outlook for Mac
• Stopped receiving emails on my account. - Microsoft Q&A
• Outlook is using a temporary email and I cannot receive emails - Microsoft Q&A
• Birthday attacks against Transport Layer Security (TLS) ciphers with 64bit block size Vulnerability (Sweet32) - Microsoft Q&A
• Outlook.com address returning TooManyObjectsOpenedError - Microsoft Q&A
• Can't send or receive email in Outlook.com
• New Outlook has stopped working, Fails when starting after 30 to 60 seconds - Microsoft Q&A