Why does the error pii_pn_b3647551c990dc41718b occur in Outlook?

This problem occurs when someone tries to access the mail server via SSL encryption, and the relationship is no longer established. Furthermore, it may be feasible that SSL encryption is disabled for the email account. There are styles of encryption provided by SMTP servers for sending and receiving emails, namely, SSL and TLS. If encryption is no longer included due to incorrect settings, the mentioned errors may be noticed.

Now, when I encounter this error, I will provide an explanation.

4 Ways to Resolve the pii_pn_b3647551c990dc41718b Error in Outlook

So, now that you’re familiar with the factors that cause the error, let’s take a look at the solutions that’ll help you troubleshoot it.

#1. Remove Duplicate Accounts

It’s quite possible that you’ve accidentally added duplicate accounts to the Outlook app and they are interfering with its normal functionality. If that’s the case, you can simply remove the duplicate accounts and this will fix the problem instantly.

Follow these steps to delete duplicate accounts in Outlook.

  • Step 1: Launch the Outlook app on your computer and tap the “Menu” button.
  • Step 2: Tap “Account Settings” and switch to the mailing tab.
  • Step 3: Now, locate the duplicate accounts and delete the repetitive entries.

Now, relaunch Outlook and check if you encounter the same error anymore or not.

#2. Change Server Port Numbers:

Another way to fix the pii_pn_b3647551c990dc41718b error is to change the server port numbers. There are many situations when users configure incorrect port numbers and encounter different types of Outlook errors.

Here’s how you can change server port numbers in Outlook.

  • Step 1: Launch Outlook and go to “FileInfo >> Account Settings >> Manage Profiles”.
  • Step 2: Then, click “Email Accounts” and double-tap the email whose server port numbers you want to change.
  • Step 3: Tap the “Advanced” tab and change the SMTP port number from 465 to 587.
  • Step 4: Click “Ok” to apply the changes.

So, that’s how you can change port numbers in MS Outlook to fix the pii_pn_b3647551c990dc41718b error.

#3. Disable Antivirus:

If you’re still encountering the error, it’s quite possible that your Antivirus program is restricting Outlook from establishing a successful connection to the server. In this situation, the only way to fix the error is to disable the Antivirus program. Keep in mind that the steps to disable the Antivirus program will vary for each user, depending on the service provider.

#4. Reinstall Microsoft Outlook:

In case none of the above-mentioned solutions work, there’s a huge probability that your Outlook app isn’t installed properly. In this case, you can either update the app to the latest version or reinstall it from scratch.


Despite being a very efficient mode of communication, electronic mails sometimes cause errors beyond our knowledge, and it becomes tough to get ut debugged. It becomes very frustrating to see the coding error and sit helplessly on the desk staring at the screen, not doing anything. Electronic mail errors can be prevented by following specific simple steps. However, the error being an AI-generated one may happen despite following the steps. When such errors occur, they can be fixed only by proper knowledge and an efficiently profound understanding of specific techniques. With an in-depth insight into the required techniques and steps to be followed, one can easily fix the electronic mail error and resume their work.

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