{"id":448758,"date":"2023-11-22T01:34:00","date_gmt":"2023-11-21T20:04:00","guid":{"rendered":"https:\/\/www.thewindowsclub.com\/?p=448758"},"modified":"2023-11-18T18:49:25","modified_gmt":"2023-11-18T13:19:25","slug":"the-server-responded-421-cannot-connect-to-smtp-outlook-error","status":"publish","type":"post","link":"https:\/\/www.thewindowsclub.com\/the-server-responded-421-cannot-connect-to-smtp-outlook-error","title":{"rendered":"The server responded: 421 Cannot connect to SMTP Outlook error"},"content":{"rendered":"

Some Outlook users have reported to be getting error 421 in Outlook<\/strong>. The full error message is as follows:<\/p>\n

The server responded: 421 Cannot connect to SMTP server<\/p><\/blockquote>\n

Many users have reported to be getting a long error message saying:<\/p>\n

Send test e-mail message: The connection to the server was interrupted. If the problem continues, contact your server administrator or Internet service provider (ISP). The server responded: 421 Cannot connect to SMTP server<\/p><\/blockquote>\n

\"The<\/p>\n

This error occurs when affected users try to send an email. Whenever they send an email, it stays in their Outbox with this error message. Now, it could be a wrong SMTP port causing the error or incorrect account configurations. Other reasons for the same can be antivirus\/firewall and VPN interferences. However, in any case, we got you covered. In this post, we will show you methods to fix the “The server responded: 421 Cannot connect to SMTP server” error. So, check out below.<\/p>\n

The server responded: 421 Cannot connect to SMTP Outlook error<\/h2>\n

If you are getting the “The server responded: 421 Cannot connect to SMTP server” error when sending emails in Outlook, here are the solutions you can use to fix it:<\/p>\n

    \n
  1. Change your SMTP settings.<\/li>\n
  2. Remove and then re-add your email account.<\/li>\n
  3. Temporarily disable your firewall and antivirus.<\/li>\n
  4. Disable your VPN, if applicable.<\/li>\n<\/ol>\n

    1] Change your SMTP settings<\/h4>\n

    The Outlook error 421 might be triggered while sending emails if you have configured an incorrect SMTP port. Many ISPs and cloud hosting providers block port 25 as it is known to be used for sending automated spam from infected PCs. Hence, if your SMTP port is set to 25, switch it to 465 and check if the error is resolved.<\/p>\n

    Here are the steps to do that:<\/p>\n

    First, open your\u00a0 Microsoft Outlook app and click on the File > Info\u00a0<\/strong>option.<\/p>\n

    Next, tap on the Account Settings <\/strong>drop-down option, and from the available options, select the\u00a0Account Settings<\/strong>\u00a0option.<\/p>\n

    In the newly opened window, choose the email account with which you are facing this error and press the Change\u00a0<\/b>button. Then, click\u00a0on the\u00a0More Settings<\/strong> button in the appeared prompt to open the Internet E-mail Settings window.<\/p>\n

    \"\"<\/p>\n

    After that, move to the Advanced<\/strong> tab, and inside the Outgoing server (SMTP)<\/strong> box, change the port number to 465.<\/p>\n

    Now, set SSL<\/strong> as the encrypted connection type.<\/p>\n

    Then, move to the Outgoing Server<\/strong> tab and make sure that the Use same settings as my incoming mail server<\/strong> checkbox is ticked.<\/p>\n

    Lastly, click on the OK<\/strong> button to apply new SMTP settings.<\/p>\n

    You can now try sending emails and check if the error 421 is fixed.<\/p>\n

    See:<\/strong>\u00a0There is a problem with the proxy server\u2019s security certificate \u2013 Outlook<\/a>.<\/p>\n

    2] Remove and then re-add your email account<\/h4>\n

    The next thing you can do is re-add your email account in Outlook and see if it helps in resolving error 421. There might be some configuration mistakes while adding an email account which is causing this error. So, remove your email account and then reconfigure your account to check if the error is fixed.<\/p>\n

    Here’s how:<\/p>\n

    First, click on the File<\/strong> menu in Outlook, and from the Info<\/strong> tab, select the Account Settings<\/strong> drop-down menu button > Account Settings<\/strong> option.<\/p>\n

    \"Remove<\/p>\n

    In the opened window, choose the problematic email account from the Email<\/strong> tab and then press the Remove<\/strong> button.<\/p>\n

    Once the email account is removed, click on the New<\/strong> button in the Account Settings window.<\/p>\n

    Now, enter your name, email address, and password, and press the Next<\/strong> button.<\/p>\n

    Follow the prompted instructions and correctly configure your email account.<\/p>\n

    When done, try sending emails and see if the error is now resolved.<\/p>\n

    Read:<\/strong> Outlook.exe Bad Image, Error Status 0xc0000020<\/a><\/p>\n

    3] Temporarily disable your firewall and antivirus<\/h4>\n

    This SMTP error could be caused due to an interference by your firewall or antivirus. If the email server IP comes under the IP ranges mistakenly blocked by your antivirus, you are likely to experience this error.<\/p>\n

    Now, to check if your security suite is the main culprit, you can briefly turn off your antivirus or firewall and see if the error is resolved. If yes, you can whitelist Microsoft Outlook through your firewall and antivirus to permanently fix the error.<\/p>\n

    To allow Outlook through Windows Defender Firewall, follow the below steps:<\/p>\n