When Does This Happen?
This issue commonly occurs during the initial account setup or when you navigate to File > Add Account in Outlook, enter your Gmail address, and hit "Connect." Outlook then tries to log in but uses an older, less secure browser engine internally—usually, Internet Explorer rather than your default browser. So, naturally, Gmail gets a bit cautious and blocks the attempt, citing security concerns.

Solution 1: Update Your Operating System

In many cases, simply installing the latest Windows updates can help. Microsoft often includes updates for compatibility and security improvements in its OS updates. However, if updating isn’t an option right now, try the registry edit solution below.

Solution 2: Force Outlook to Use a Supported Browser Engine

If updating isn’t possible or doesn’t resolve the issue, follow these steps to manually tweak Outlook's settings in the registry:

1. Open the Registry Editor

   • Press Windows key + R to open the Run dialog.
   • Type regedit and hit Enter.

2. Navigate to the Registry Key

   • In the Registry Editor, go to: Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_BROWSER_EMULATION

3. Add a New DWORD Value

   • Right-click in the main pane, select New > DWORD (32-bit) Value.
   • Name the new value OUTLOOK.EXE.
   • Set the Value Data to 11000 in decimal form (this enables IE 11 mode, which is compatible with Google sign-in).

4. If Needed, Add Additional Keys

   • If the error persists, try adding the same OUTLOOK.EXE entry with the value of 11000 in these locations as well:
   • Current User Key: Computer\HKEY_CURRENT_USER\SOFTWARE\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_BROWSER_EMULATION
   • 32-Bit Emulation Key (for 64-bit systems): Computer\HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_BROWSER_EMULATION

These settings tell Outlook to use the IE 11 compatibility mode, which should satisfy Gmail’s security requirements and allow you to complete the login process.

Problem Solved? Let’s Celebrate (Safely)!

And just like that, Gmail should now connect to Outlook without any complaints. Comment below if you’ve had success with this or if something’s still holding out. And hey, at least Gmail cares enough to make sure we’re logging in "securely"—even if it does mean asking us to dance with Internet Explorer now and then.