Start by checking that your device is online and Outlook is not set to Work Offline. Then try signing in to your mailbox in a browser. If webmail works, focus on Outlook’s settings or sign-in; if it does not, check with your email provider or work/school administrator before changing server details.
Why is Outlook not connecting to the server?
The cause may be your internet connection, Outlook’s offline state, account settings or authentication, a firewall or proxy, or an unavailable mail service. The quickest way to narrow it down is to check the connection, test the mailbox in webmail, and then troubleshoot the app or account type that is failing.
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How to troubleshoot Outlook in order
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Confirm internet access and Outlook’s status
Open a browser and load a website. If other sites do not load, address the device or network connection first. Restarting the network connection or device can help diagnose a connection problem, but it is not a guaranteed Outlook fix.
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Test the mailbox in a browser
Sign in to your provider’s webmail, such as Outlook on the web for a Microsoft Exchange mailbox. If webmail also fails, the issue may involve the account or mail service; check the provider’s service status or contact its support team. For a work or school Exchange mailbox, ask the administrator to check service availability.
If webmail works, the mailbox is reachable outside the Outlook app. Continue with Outlook’s online/offline state, account configuration, or authentication. For Exchange on Mac, Microsoft recommends trying another Exchange application, such as Outlook on the web, and checking server status with the administrator: Microsoft’s Exchange connection troubleshooting.
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Confirm settings with the email provider
If you added a POP or IMAP account manually, check the provider’s current instructions for the incoming and outgoing server names, ports, encryption (SSL/TLS), username, and password. Some providers require SMTP authentication, and some networks or internet providers block particular outgoing mail servers. Ask the email provider or network administrator for supported settings instead of trying generic server names or ports.
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Resolve repeated password prompts carefully
If Outlook.com repeatedly requests your password, the sign-in method may be the issue. Microsoft documents a problem involving Outlook.com accounts configured with Basic authentication and provides OAuth-compatible setup guidance. The supported method depends on the Outlook version and whether the account is connected directly or through POP/IMAP. Microsoft says direct Outlook.com connections support OAuth in the listed current Microsoft 365 and Outlook 2021 LTSC configurations, while its described Outlook.com POP/IMAP setup does not support OAuth. Check the version and connection method before changing the account: Microsoft’s Outlook.com authentication guidance.
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For Exchange on Mac, check organization-specific requirements
In Outlook for Mac, open Tools > Accounts and review the account and its connection indicator. Microsoft lists incorrect credentials or server name, Work Offline, network availability, Exchange server availability, required encryption, and a mail proxy among possible connection causes. Encryption and proxy settings depend on the organization, so ask the Exchange administrator for the correct requirements.
Do not empty an Exchange cache as an early troubleshooting step. Microsoft warns that clearing it can remove information that has not synchronized, including a mail certificate. See Microsoft’s Exchange connection troubleshooting.
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For mobile problems, distinguish email sync from full account sync
POP and IMAP sync email, not calendars or contacts. If mobile setup asks for server details, get them from the email provider. Microsoft directs users with Microsoft 365 work or school and Exchange accounts to their administrator, Outlook.com users to Microsoft, and users of Gmail, Yahoo, iCloud, and other non-Microsoft accounts to the relevant provider for account or sign-in support. See Microsoft’s mobile Outlook setup guidance.
What to do if Outlook says “Disconnected” or “Trying to connect”
First confirm the device has internet access, then check whether Work Offline is enabled. Test the mailbox in webmail before altering settings. If webmail works but Outlook remains disconnected, check the account’s configuration and authentication; for a work or school Exchange account, ask the administrator about server availability, proxy, encryption, or other organization-specific requirements.
Check for a known issue when the error matches
Microsoft’s Outlook for Mac known-issues page lists a specific problem affecting some @shaw.ca and Rogers-domain accounts: users may be unable to send or receive mail in legacy or new Outlook, with SMTP error “-3253” or a dropped connection. The page was last updated June 18, 2026, and showed the issue as under investigation when inspected October 7, 2026. Its status may change; check the live Outlook for Mac known-issues page if those exact symptoms and account types apply. This report does not establish that other providers or all Mac users are affected.
Which support team should you contact?
- Microsoft 365 work/school or Exchange: Contact your administrator to verify service availability, account requirements, proxy, and encryption settings.
- Outlook.com: Contact Microsoft if the mailbox or sign-in fails beyond the Outlook app.
- Gmail, Yahoo, iCloud, or another provider: Contact that provider for current server settings and account or sign-in support.
- Only Outlook fails while webmail works: Focus on the Outlook app’s status, account setup, or authentication rather than assuming the mail server is down.
Microsoft also states that ActiveSync versions earlier than 16.1 can no longer connect to Microsoft services starting March 1, 2026. This compatibility cutoff matters when diagnosing an older mobile mail setup; it is not a general explanation for every Outlook connection failure. See Microsoft’s server-settings guidance.
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