pii_email_864625849f4d9cdad180 Error: 7 Best Fixes (2026)

Seeing the pii_email_864625849f4d9cdad180 error in Outlook and unable to send or receive emails? You are not alone — this is one of the most common Outlook error codes reported by Microsoft 365 users. The quick answer: this error is usually caused by a corrupted Outlook cache, duplicate email accounts, or incorrect SMTP server settings. Clearing your cache, signing out of all accounts, and removing duplicates fixes it in most cases.

If those quick fixes do not work, this guide walks you through seven tested methods — from verifying your SMTP port settings to running a full Microsoft 365 repair — so you can resolve the [pii_email_864625849f4d9cdad180] error step by step. Every method below is written for the current versions of Outlook in 2026, including the new Outlook for Windows and classic Outlook with Microsoft 365.

What causes the [pii_email_864625849f4d9cdad180] error in Outlook?
How to resolve [pii_email_864625849f4d9cdad180] error: 7 working methods
How to prevent pii_email errors in Outlook
FAQs
Conclusion

What causes the [pii_email_864625849f4d9cdad180] error in Outlook?

The [pii_email_864625849f4d9cdad180] error is a client-side error, which means the problem sits on your computer or in your Outlook configuration — not on Microsoft’s servers. Outlook generates these pii_email codes when it detects a personal-information processing fault: something in your local data files, account setup, or program installation is stopping Outlook from handling your mail correctly.

The most common triggers are:

Corrupted cache and cookies. Over time, Outlook stores cached credentials and temporary data. When this cache becomes corrupted, Outlook throws the pii_email_864625849f4d9cdad180 error instead of signing you in properly.
Multiple or duplicate accounts. If the same email account is added twice, or several accounts conflict with each other, Outlook cannot decide which profile to use and displays the error.
Wrong SMTP server settings. Incorrect outgoing server (SMTP) details — the wrong port number or encryption type — prevent Outlook from sending mail and can trigger this code.
Outdated Outlook version. Running an old build of Outlook alongside a newer Microsoft 365 installation often creates compatibility faults that surface as pii_email errors.
Antivirus or firewall interference. Security software with aggressive email scanning can block Outlook’s connection to the mail server.
Damaged installation files. If core Microsoft 365 files are corrupted — after a failed update or a sudden shutdown — Outlook may fail to start your profile correctly.

The good news is that every one of these causes has a straightforward fix. Work through the methods below in order, starting with the simplest.

How to resolve [pii_email_864625849f4d9cdad180] error: 7 working methods

Start with Method 1 and move down the list. Most users resolve the pii_email_864625849f4d9cdad180 error within the first three methods.

1. Clear the cache and sign out of all Outlook accounts

A corrupted cache is the single most common cause of this error, so this is always the first thing to try. Clearing it forces Outlook to rebuild its temporary data from scratch.

Close Outlook completely. Check the system tray (bottom-right corner of Windows) and right-click the Outlook icon, then choose Close if it is still running.
Open the new Outlook for Windows and click the Settings gear icon at the top-right.
Go to General > Storage and note how much cached data Outlook is holding.
Click Empty next to cached data to clear it, then close Settings.
Still in Outlook, click your profile picture at the top-right and choose Sign out. If you use multiple accounts, sign out of every one of them.
Restart your computer. This is important — it clears any Outlook processes still holding the old cache in memory.
Open Outlook again and sign back in with your primary account. Check whether the [pii_email_864625849f4d9cdad180] error is gone.

If you use classic Outlook, you can also delete the local cache manually: press Windows + R, type %localappdata%\Microsoft\Outlook, and delete the contents of the RoamCache folder. Do not delete your .ost or .pst data files — only the RoamCache folder.

2. Check for duplicate accounts and remove them

Duplicate accounts are the second most common trigger. When the same mailbox appears twice in your profile, Outlook’s sync engine conflicts with itself and raises the pii_email_864625849f4d9cdad180 error.

In the new Outlook for Windows, click the Settings gear icon and go to Accounts > Email accounts.
Review the full list carefully. Look for the same email address appearing more than once, or old accounts you no longer use.
Click Manage next to any duplicate or unwanted account, then choose Remove.
If you use classic Outlook, go to File > Account Settings > Account Settings, select the duplicate on the Email tab, and click Remove.
Restart Outlook and test sending and receiving mail.

Removing a duplicate account does not delete your emails — your messages stay on the mail server and will re-sync. If the error disappears after this step, you have found your cause.

3. Verify SMTP server settings and port numbers

Wrong outgoing mail (SMTP) settings are a classic cause of Outlook errors. The correct values depend on your provider, but the standard secure settings in 2026 are:

Outgoing server (SMTP): port 587 with STARTTLS encryption, or port 465 with SSL/TLS encryption.
Incoming server (IMAP): port 993 with SSL/TLS encryption.
“My outgoing server (SMTP) requires authentication” must be checked, using the same credentials as your incoming server.

In classic Outlook, go to File > Account Settings > Server Settings.
Select your account and open the outgoing mail (SMTP) section.
Confirm the port is set to 587 (preferred) or 465, with the matching encryption type selected.
Make sure SMTP authentication is enabled with your full email address and password.
Click Next > Done, then restart Outlook and send a test email.

In the new Outlook for Windows, go to Settings > Accounts > Email accounts, click Manage on your account, and review the server settings there. Fixing a wrong port here resolves the [pii_email_864625849f4d9cdad180] error surprisingly often — many users inherit incorrect settings when an account is auto-configured.

4. Run a Microsoft 365 repair from the Control Panel

If the error persists, the Outlook installation itself may be damaged. Microsoft’s built-in repair tool fixes corrupted program files without touching your emails or settings. See Microsoft’s official Outlook support pages for the latest repair documentation.

Close Outlook and all other Microsoft 365 apps (Word, Excel, Teams).
Open the Control Panel (press Windows + R, type control, and press Enter).
Go to Programs > Programs and Features.
Find Microsoft 365 (or Microsoft Office) in the list, right-click it, and choose Change.
Select Quick Repair first and click Repair. This takes a few minutes and fixes most issues.
If the pii_email_864625849f4d9cdad180 error is still there, repeat the steps but choose Online Repair instead. This downloads fresh installation files, so it needs an internet connection and takes longer.
Restart your computer, open Outlook, and check whether the error is resolved.

Online Repair is the deeper fix and resolves most stubborn cases of this error code. It is safe: your accounts, emails, and rules are preserved.

5. Update Outlook to the latest version

Running an outdated Outlook build is a well-known trigger for pii_email errors. Microsoft regularly patches the exact profile and sync bugs that cause codes like [pii_email_864625849f4d9cdad180].

In classic Outlook, go to File > Office Account.
Under Product Information, click Update Options > Update Now.
Wait for the update to download and install, then restart Outlook.
For the new Outlook for Windows (installed from the Microsoft Store), open the Microsoft Store app, go to Library, and click Get updates.
Also run Windows Update (Settings > Windows Update > Check for updates), since Outlook depends on current Windows components.

After updating, sign out and back in once so the new build re-authenticates your accounts cleanly.

6. Check antivirus and firewall interference

Security software with email scanning or SSL interception can block Outlook’s connection to the mail server, producing the pii_email_864625849f4d9cdad180 error even when everything else is configured correctly.

Open your antivirus program and look for an email shield, mail scanning, or SSL scanning option.
Temporarily disable email/SSL scanning only (keep real-time file protection on).
Restart Outlook and test whether the error is gone.
If the error disappears, re-enable scanning and instead add Outlook as an exception: in your antivirus settings, add outlook.exe to the exclusions list, or whitelist the Outlook data folder.
Check Windows Defender Firewall too: go to Control Panel > System and Security > Windows Defender Firewall > Allow an app through firewall, and make sure Outlook is allowed on private and public networks.

Never leave your antivirus fully disabled as a permanent “fix” — use targeted exceptions instead. If you are unsure which setting is blocking Outlook, your antivirus vendor’s support pages explain the exact exclusion steps.

7. Reinstall Outlook as a last resort

If none of the six methods above cleared the [pii_email_864625849f4d9cdad180] error, a clean reinstall removes every corrupted file and registry entry in one go.

Back up anything stored only locally: in classic Outlook, go to File > Open & Export > Import/Export and export to a .pst file if you use POP3. (IMAP and Microsoft 365 accounts keep everything on the server, so no backup is needed.)
Open Control Panel > Programs > Programs and Features, right-click Microsoft 365, and choose Uninstall.
Restart your computer.
Sign in at office.com with your Microsoft account and reinstall Microsoft 365, or reinstall the new Outlook from the Microsoft Store.
Open Outlook, add your email account fresh, and let it fully sync before judging the result.

A reinstall takes 15–30 minutes but resolves virtually every remaining instance of this error. Similar multi-step troubleshooting also works for related codes — for example, our guide to fix [pii_email_8fac9ab2d973e77c2bb9] error follows the same repair logic for a different error code.

How to prevent pii_email errors in Outlook

Once the pii_email_864625849f4d9cdad180 error is gone, a few habits keep it from coming back:

Keep Outlook updated. Enable automatic updates so you always run a build with the latest sync and profile fixes. Outdated builds are the number one recurring cause.
Use one account per mailbox. Never add the same email address twice. If you need a mailbox on two devices, add it once per device — duplicates inside a single profile are what cause conflicts.
Do not change SMTP settings manually unless needed. Auto-configured settings are correct for Gmail, Outlook.com, and Microsoft 365. Manual edits with the wrong port are a frequent self-inflicted cause.
Clear the cache periodically. Signing out and back in every few months, or clearing cached data via Settings > General > Storage, prevents the slow corruption that leads to pii_email errors.
Whitelist Outlook in your antivirus from day one. Adding outlook.exe as an exclusion when you first install your security software avoids the interference described in Method 6.
Shut down Outlook properly. Forcing your PC off while Outlook is syncing can corrupt data files. Close Outlook before shutting down.

These same prevention steps apply across the whole family of Outlook personal-information errors. If you ever hit a sibling code, the walkthrough to fix [pii_email_e9d48ac2533bded18981] error uses identical prevention principles.

FAQs

What is the [pii_email_864625849f4d9cdad180] error in Outlook?

It is a client-side Outlook error code indicating a personal-information processing fault in your local Outlook setup. It is triggered by corrupted cache, duplicate accounts, wrong SMTP settings, outdated builds, or damaged installation files — never by a problem on Microsoft’s servers.

Will I lose my emails if I reinstall Outlook to fix this error?

No, as long as you use IMAP or a Microsoft 365/Exchange account, all your emails stay on the server and re-download after reinstalling. Only POP3 accounts store mail locally, so export a .pst backup first if you use POP3.

Why does the pii_email_864625849f4d9cdad180 error keep coming back after I fix it?

Recurrence almost always means the root cause was not addressed: an outdated Outlook build that needs updating, an antivirus that keeps interfering, or a duplicate account that was re-added. Work through the prevention steps above — especially updates and antivirus exclusions — to stop the cycle.

Can I fix this error on the Outlook mobile app?

The pii_email_864625849f4d9cdad180 error is specific to Outlook on Windows (desktop). If the mobile app shows a sign-in problem, remove the account from the app and add it again — that resolves nearly all mobile-side issues.

How long does the Microsoft 365 Online Repair take?

Quick Repair takes 5–10 minutes; Online Repair takes 20–40 minutes depending on your internet speed, since it re-downloads installation files. Your emails and settings are preserved in both cases.

Conclusion

The pii_email_864625849f4d9cdad180 error looks alarming, but it is one of the most fixable Outlook problems: in most cases, clearing the cache, signing out of all accounts, and removing duplicates resolves it in under ten minutes. If those quick steps fail, verifying your SMTP ports, running a Microsoft 365 repair, updating Outlook, and checking antivirus interference cover every remaining cause — with a clean reinstall as the final fallback.

Work through the seven methods in order, apply the prevention habits once you are back up and running, and this error code should not bother you again. If a different pii_email code appears in the future, the same troubleshooting logic applies.