421 cannot connect to smtp server

421 cannot connect to smtp server

When you see the 421 cannot connect to smtp server message on the Outlook application, proceed with the solutions provided here to resolve it.

Solution 1 - Re-Configuring The SMTP Server Settings

  • Step 1:Open the MS Outlook application by clicking its icon on the desktop of your computer.
  • Step 2:In the main interface of the MS Outlook application, click the File tab that is located at the left end of the screen.
  • Step 3:When you see the Account Information window, select Account Settings from the Account Settings drop-down list.
  • Step 4:Select the name of your email account and click the Change button to display the Change Account window.
  • Step 5:Navigate to the Server Information section and fill the Outgoing Mail Server (SMTP) field for 421 cannot connect to smtp server.
  • Step 6:Click More SettingsOutgoing ServerMy Outgoing server (SMTP) requires authenticationUse same settings as my incoming mail server.
  • Step 7:Click OK in the Internet Email Settings window.
  • Step 8:Navigate back to the Internet Email Settings window and click the Advanced tab.
  • Step 9:In the Outgoing Server field, type the port number as either 465 (SSL) or 587(TLS).
  • Step 10:Make sure to select the SSL/TLS protocol from the ‘Use the following type of encrypted connection’ drop-down menu.
  • Step 11:Click OKSave Settings.
  • Step 12:Check if the error is rectified by sending an email from the Outlook application.
  • Step 13:If the ‘error: 421 cannot connect to SMTP server’ persists, carry out the remaining solutions mentioned below.

Solution 2 - VPN Interference

  • Step 1:This error might occur due to VPN interference.
  • Step 2:Disable the VPN service and try to send the email after the completion of 421 cannot connect to smtp server.
  • Step 3:If the issue is resolved, the VPN is probably the reason for this error.
  • Step 4:Otherwise, perform the alternative solution provided here.

Solution 3 - Antivirus Interference

  • Step 1:Disable your antivirus or firewall on your computer.
  • Step 2:Now, check if you can send the email without any issue.
  • Step 3:If the issue is resolved, the cause for this problem is the antivirus interference with the Outlook application.
  • Step 4:Every time you send the email, disable the antivirus program running on the computer.
  • Step 5:When you are not able to clear the 421 cannot connect to smtp server, get help from our technical experts.
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