VPNs are used in the following situations: If the problem persists and you still cannot send the email, try the next solution. Click ok and apply and close the program. Go to the Advanced tab and then change the port number provided by your ISP. Now, re-expand the Advanced Settings window.
Then select the "My outgoing mail server (SMTP) requires authentication" checkbox and select Use the same settings as my incoming mail server option. Next, open "Advanced Settings" and go to the Outgoing Mail Server tab. Now, enter the address (provided by your web host). Now, click the "Change" button and find "Outgoing Mail Server (SMTP)". Next, select "Account Settings" on your account. Launch MS Outlook and click the "File" button. To check and change SMTP settings in Microsoft Outlook, do the following: Since misconfiguration in SMTP is the most common cause of this problem, the first step is to check the configuration. Here are few methods that can be helpful and any of them can be your solution. Let's fix 'Outlook error 421 cannot connect to smtp' issue Plus, you can protect your mail, restore it when needed, and more. In this article, you will find many great methods to remedy the situation and be able to send a test email message. However, many other factors can cause this problem. The most common cause of “outlook 421 cannot connect to smtp” is incorrect SMTP configuration. The error “outlook 421 cannot connect to smtp outlook 2007” is mainly related to Microsoft Outlook accounts and occurs when sending an email message through Microsoft Outlook.