--- title: "Outlook error 0x800CCC0E: “Cannot connect to the server” on an IMAP account" description: "Classic Outlook stops syncing an IMAP account and reports error 0x800CCC0E, \"Cannot connect to the server\". The error only says Outlook could not reach or sign in to the mail server. Here is how to tell a Microsoft-documented Gmail or Yahoo sign-in problem from a wrong port, a blocked port or antivirus mail scanning, with the least invasive fix first." url: "https://keh-tech.net/kb/outlook-error-0x800ccc0e-cannot-connect-to-server/" updated: "2026-10-05" category: Troubleshooting tags: - Credential Manager - IMAP - Microsoft 365 - Microsoft Outlook - PowerShell - Windows --- # Outlook error 0x800CCC0E: “Cannot connect to the server” on an IMAP account Outlook has been fine for months, then Send/Receive starts failing on one IMAP account with this message: ``` Task 'Synchronizing subscribed folders for you@example.com.' reported error (0x800CCC0E) : 'Outlook cannot synchronize subscribed folders for you@example.com. Error: Cannot connect to the server. If you continue to receive this message, contact your server administrator or Internet service provider (ISP).' ``` You may see the same code on the Inbox, Sending or Receiving tasks instead. Webmail for the account still works, the internet is up, and the password is right. The error is deliberately vague: it means Outlook could not **reach** the mail server or could not **sign in** to it. This article separates the causes so you fix the right one. **Applies to:** classic Outlook for Windows with an **IMAP** account (Gmail, Yahoo, Microsoft 365 or Outlook.com over IMAP, a hosting company or an ISP). The new Outlook is not covered here. ## What is going on IMAP is the protocol Outlook uses to read mail from a server and keep folders in step. SMTP is the separate protocol it uses to send. Each one opens a network connection to the provider's server on a particular **port**, usually wraps it in encryption (**SSL/TLS**, or **STARTTLS** which switches on encryption after connecting), and then signs in. Error 0x800CCC0E is Outlook reporting that one of those steps did not complete. It does not say which. There are four common reasons, and they need different fixes: - **A stale sign-in token.** Gmail and Yahoo mailboxes use OAuth sign-in in classic Outlook, where Outlook stores a token in Windows rather than your password. Microsoft documented a problem from 26 February 2026 where this produced 0x800CCC0E and 0x800CCC0F and Outlook did not prompt for a new sign-in. Microsoft says it was fixed by 20 March 2026 through a Microsoft 365 service update, and that a password change could bring the error back. - **Wrong server, port or encryption.** The most common cause with hosting and ISP mailboxes, and after a provider changes its rules. - **A blocked port.** A firewall, a network or an ISP stopping the connection. - **Security software** that scans or intercepts mail connections. ## Diagnosis ### 1. Check webmail, then another network Sign in to the account in a browser. If that fails, fix the account first (password, security prompts from the provider, an app password if the provider requires one) before touching Outlook. If webmail works, try Outlook from another network, such as a phone hotspot. If it works there, your normal network or ISP is blocking the connection and no Outlook setting will fix it. ### 2. Test the connection from the PC Use your provider's published server names. Replace the examples below. As a Microsoft example, Microsoft 365 / Exchange Online uses `outlook.office365.com` port 993 (IMAP, SSL/TLS) and `smtp.office365.com` port 587 (STARTTLS). ``` Test-NetConnection outlook.office365.com -Port 993 Test-NetConnection smtp.office365.com -Port 587 ``` Look at `TcpTestSucceeded`. **True** means the port is reachable, so the problem is encryption settings, the sign-in or software on the PC. **False** means the connection is being blocked or the host name is wrong. This test only proves the port opens; it does not prove the sign-in works. ### 3. Read the account settings In Outlook, choose **File > Account Settings > Account Settings**, double-click the account, and check the incoming and outgoing server names. Then select **More Settings > Advanced**. Compare against what your provider publishes, not against an old email. Typical values: - **Incoming (IMAP):** port **993**, encryption **SSL/TLS**. - **Outgoing (SMTP):** port **587** with **STARTTLS**, or port **465** with **SSL/TLS**, whichever your provider documents. Do not use port 25; many ISPs block it. - On **More Settings > Outgoing Server**, tick **My outgoing server (SMTP) requires authentication** and **Use same settings as my incoming mail server**. ### 4. Think about who made the account If it is a Gmail or Yahoo account that stopped syncing suddenly, or after a password change, it fits the sign-in token problem Microsoft documented. If it is a hosting or ISP mailbox that has never worked, or stopped after you changed a port, look at steps 2 and 3. Providers also change what they accept: some now require an **app password** (a separate password you generate in the provider's security settings) instead of your normal one. Check the provider's own help pages for which they require. ## Root cause For Gmail and Yahoo in 2026, Microsoft attributed a spike in these errors to a defect that was fixed by a service update, with a leftover stored sign-in token as the trigger. For every other IMAP mailbox the cause is local to you: the wrong server or port, a blocked port, an app-password requirement, or security software. In all cases Outlook is only reporting that it could not connect. ## The fix ### A. Gmail or Yahoo: clear the stored sign-in (least invasive) This follows Microsoft's documented workaround and does not delete any mail. Close Outlook first. 1. Open **Credential Manager** from the Start menu and select **Windows Credentials**. 2. Find the entries that begin with `MicrosoftOffice16_Data:OAUTH2`. Remove the ones that contain `tp_google_imap_Oauth2` (Gmail) or `tp_yahoo_imap_Oauth2` (Yahoo). 3. Start Outlook and sign in to the account again when it asks. If it does not prompt, restart Outlook once more. Microsoft says Outlook may not prompt for a new sign-in for about an hour after a password change; clearing the entries forces it. ### B. Correct the settings and ports Fix whatever step 3 showed does not match your provider, close the dialog and let Outlook run its test. If step 2 returned `TcpTestSucceeded : False` on the right port, no setting will help; raise it with the network owner or the ISP, or use a different network. ### C. Check antivirus email scanning Some antivirus products scan mail by inserting themselves into the encrypted connection. Microsoft's documentation says antivirus integration with Outlook can cause problems and advises excluding Outlook from it where needed, at your own risk. The sensible test is to switch off **only** the email-scanning or "mail shield" component for a few minutes, press `F9`, and then switch it back on. If that cures it, do not leave it off: add an exclusion for Outlook in the product's settings or ask the vendor. Do not disable your antivirus as a whole. ### D. IMAP folders and timeouts (only if the error is about a folder) If connecting works but one folder will not sync, right-click the account name and choose **IMAP Folders** (also on the Send/Receive tab), clear **When displaying hierarchy in Outlook, show only subscribed folders**, select **Query**, and subscribe only to the folders that really exist on the server. Raising the **Server Timeouts** slider on **More Settings > Advanced** to a few minutes can help on a slow link, but it will not cure a block or a bad sign-in. ### E. Last resort for Gmail or Yahoo: delete the identity key **You are editing the registry.** Close Outlook. In Registry Editor, go to `HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity\Identities`, right-click the key, choose **Export** and save it. Then delete **only** the subkey that belongs to the affected address. Restart Outlook and sign in again. This is Microsoft's second documented workaround, for when the Credential Manager step has not worked. Do not delete the parent Identities key or other accounts' subkeys. ### F. Remove and re-add the account Only after the above. An IMAP account's mail lives on the server, but Outlook can hold items that were never synced, so check the web mailbox first and export to a PST if there is anything you cannot afford to lose. Re-adding the account in a fresh profile is a bigger step than the ones above, so it should not be your first move. ## Verification Press `F9` (Send/Receive All Folders). Open the progress window and confirm that both the sending and the "Synchronizing subscribed folders" tasks finish with no error. Send yourself a message and make sure it arrives and shows up in the Sent Items folder. If the fix involved Gmail or Yahoo, check again after about an hour, because token problems can look fixed until the old token expires. ## Notes - **Why not NTLM or "Secure Password Authentication"?** Those are for providers that specifically ask for them. Gmail and Yahoo do not, and changing the method will not fix a connection error. Only change it if your provider's own instructions say so. - Do not delete and rebuild the whole Outlook profile before checking ports and sign-in. It takes much longer and cures none of the causes above. - Ports 993 and 587 are the usual values. Treat port 143 or an unencrypted connection as suspect unless your provider documents it. - The same code can also be reported for SMTP or POP accounts. The checks in steps 1 to 3 apply to them too. - Several users at one site with the same error: suspect the firewall, web filter or antivirus policy before the individual profiles. **Not matching any of these?** Post the exact error line (leave your address out), the provider name and the result of `Test-NetConnection` in [The Patch Panel](/community/help/), and we will take it from there. The best answer earns points on [Top of the Stack](/leaderboard/).