Do you know how to fix Outlook 421 cannot connect to SMTP server error? Still clueless about why you see Outlook error code 421? If yes, then you landed at the right blog!

We through this blog will cater to your issues like what causes Outlook error code 421. Furthermore, we’ll discuss how to fix Outlook 421 cannot connect to SMTP server error?

For those who don’t know, Outlook error code 421 is a common SMTP  error that occurs when trying to send an email in Outlook. Additionally, it occurs as a result of:

• Antivirus program on your PC intervening in Outlook
• IMAP Outlook accounts with faulty SMTP configurations

Let us now see what causes SMTP response 421.

Causes: Why Do I See SMTP Response 421?

The solution for a problem starts only after knowing its cause. The same goes with SMTP error (421) connection to server failed cpanel.

Therefore, before proposing a solution of How To Fix Outlook 421 Cannot Connect To SMTP Server Error, firstly, let’s know its cause.

Here are a few reasons behind the occurrence of error SMTP response 421:

• Faulty Outlook Configurations: This counts for a major reason behind smtp error (421) connection to server failed. Furthermore, recent email configurations lead to this issue.
• Automated blocked traffic to block users from spam networks, from port 25 &26
• 3rd party firewalls block connections to some IP ranges
• Virus interference
• Corrupted PST files

Now that we know the causes, let’s find out How To Fix Outlook 421

Cannot Connect To SMTP Server Error?

How To Fix Outlook 421 Cannot Connect To SMTP Server Error?

We went through some of the reasons behind the occurrence of could not connect to SMTP host response: 421

Hence, now we’ll be sharing some tricks, for how to fix Outlook 421 cannot connect to SMTP server error. 

Moreover, the methods are simple, easy to understand and takes relatively less time in fixing connect error 421.

Therefore, read below to know how to fix Outlook 421 cannot connect to SMTP server error.

• Method 1: Reconfigure SMTP Settings 

This gets counted as one of the most common reasons behind smtp error 421 connection to server failed.

It probably happens when there is some improper existing SMTP configuration.

So, what next? All you need to do is simple. Just check your configuration settings and reconfigure them.

Thereafter you’ll get familiar with how to fix Outlook 421 cannot connect to SMTP server error.

We recommend you to go for Stellar Outlook PST Recovery Software to fix SMTP response 421.

• Method 2: Disable Your VPN, For A While

Undoubtedly, VPNs give you that holy perk! 100% access to all geo-blocked web services for free! Further, also keeping you safe by hiding your location.

They do a lot, don’t they?

However, these VPNs at times become a bone of contention.

Wondering how it can cause sending’ reported error (0x800ccc67) ‘ the server responded 421 cannot connect to SMTP server?

VPNs intrude in browsing activities. As a result, it may also intrude in the entire set of activities carried out in Outlook. It includes your accessibility and transfer of emails in Outlook.

Hence, to resolve the same, put your VPN mode off and aside for a while. Thereafter try sending out the emails in the normal mode.

• Method 3: Disable Antivirus or Firewall 

Conventionally known for safeguarding your system from vicious files, this software can sometimes be the reason behind SMTP response 421.

Many 3rd party firewalls antivirus forbids some IP ranges, including email servers.

Therefore, disabling both Firewalls and Antivirus for a while can be a better option to resolve Outlook error code 421.

Note: You don’t have to disable your firewall or antivirus if your system has an inbuilt Windows firewall. Why? Because in that case they are not installed from any 3rd party sites.

• Method 4: Remove and  Re-add your Email Account

First thing first. DO NOT forget to click on Auto Account Setup instead of the manual one.

Yes, sometimes the glitch is due to the newly added email account.

Well, don’t panic as all you need to do is remove your email account and add it again. Simple as that!

Therefore, this is one of the ways of how to fix SMTP error.

• Method 5: Change SMTP Port Number

Okay, so you tried all of the above-mentioned methods.

However, you still couldn’t fix How to fix Outlook 421 cannot connect to SMTP server error?

Well, in that case, you should think about your SMTP port number.

Yes, your SMTP port number. Chances are that faulty SMTP configuration is the culprit behind connect error 10060

Hence, we why not once change SMTP port number to fix SMTP error (421) connection to server failed.

So far, we talked about the causes of SMTP response 421.

Thereafter, we dealt with in detail, how to fix Outlook 421 cannot connect to SMTP server error.

Stellar Outlook PST Recovery Software

PST files index all your important documents and files like events, copies of messages, calendars, etc, from your mailbox.

However, if these files get corrupted, it can invite errors including Outlook error code 421. 

In such cases, you may want to repair the PST files.

Wait, not able to access Outlook’s in-built utility? Well, hang in there! There’s a way for that too!

When it comes to recommending software, we suggest the best.

Stellar Outlook PST Recovery Software is the best tool to retrieve all your important but lost mailbox data.

Why Go For Stellar Outlook PST Recovery Software?

Stellar Outlook PST Recovery Software can easily deal with your severely corrupted PST files. It is quick, convenient, and has inherent excellent algorithm skills which bring back all your important attachments.

Features Of Stellar Outlook PST Recovery Software

Here are some of the excellent features of Stellar Outlook PST Recovery Software

• Easiest recovery of Outlook PST
• Backup of deleted of your Outlook data
• Preview of the recoverable data
• Split or Compact PST & export to Office 365

Summing Up

We through this blog informed you about the causes of SMTP response 421. Furthermore, we even discussed how to fix Outlook 421 error cannot connect to SMTP server error.

Not just this but we also suggested you the best repair tool to fix this error. In conclusion, we hope you found this piece helpful!