Resolve Mozmapi32.dll Error When Installing Thunderbird

The mozmapi32.dll file is created by Mozilla, Netscape and is an important component of the Thunderbird e-mail client. By default, the mozmapi32.dll file is located in the C:\Program Files\Mozilla Thunderbird folder.

In this article, we will discuss a few instances of the mozmapi32.dll error that you may come across while installing, updating, or uninstalling Thunderbird.

Error 1

While installing or updating Thunderbird, the installation or updation process fails and you may receive the following error:

“C:\Program Files\Mozilla Thunderbird \mozMapi32.dll. Click retry or cancel the installation"

Cause of the Error

The above error typically occurs when you have Logitech webcam installed on your computer. There is a known issue between Logitech webcam and Thunderbird.

The above mozmapi32.dll error occurs if you have set Thunderbird as the default email program in the Quickcam software. Quickcam does not let Mozilla update the mozmapi32.dll file, causing the above error message to appear.

Resolution Methods

To resolve the mozmapi32.dll error, use either of the following methods.

Method 1: Disable the Logitech webcam software

To disable the Logitech webcam software, perform the following steps:

  1. Right-click the Quickcam icon in your system tray.
  2. Next, select Exit.

After you have disabled the Quickcam, install or update Thunderbird.

Method 2: Rename the mozmapi32.dll file

To rename the mozmapi32.dll file, perform the following steps:

  1. Double-click the My Computer icon on your desktop.
  2. Browse to the folder C:\Program Files\Mozilla Thunderbird and locate the mozmapi32.dll file.
  3. Right-click mozmapi32.dll and rename it to mozmapi32.old.dll.

After you have renamed the mozampi32.dll, continue the updating process for Thunderbird.

Method 3: Temporarily set a different email program as Quickcam’s default email program

To resolve the above mozmapi32.dll error, temporarily set Quickcam to use a different email program as the default. After you have installed or updated Thunderbird, you can set Thunderbird as Quickcam’s default email program.

Error 2

On a Windows Vista computer, when you try uninstalling Thunderbird via Vista Uninstall, the process fails to completely uninstall Thunderbird. If you try to manually delete the Thunderbird folder, you are unable to delete the mozmapi32.dl file and the following error message is displayed:

"Destination Folder Access Denied. You need permission to perform this operation."

The above error appears even if you are logged in with administrative rights.

Cause of the Error

Typically, the above error occurs if you have a Logitech webcam installed.


To resolve the issue, temporarily disable Quickcam and proceed with unisntallation. After you have uninstalled Thunderbird, you may enable Quickcam.

Besides issues with Logitech webcam, other common causes of mozmapi32.dll errors are malware infection and registry issues.

Malware programs, such as virus, rootkits, backdoors, worms, and trojans, if present on your computer, can corrupt your DLLs by injecting invalid codes into them. As a result, if the mozmapi32.dll file on your computer is corrupt, you may receive a mozmapi32.dll error every time an application tries to access this file. To fix mozmapi32.dll errors occurring due malware infection, scan your entire computer using advanced security software, such as STOPzilla Antivirus and Spyware Cease.

Registry problems may also cause recurring mozmapi32.dll errors. To prevent and fix DLL errors occurring due to a bad or corrupt registry, regularly scan your registry using reliable registry cleaning software, such as RegServe. It is a powerful tool that removes all incorrect registry entries with just a few mouse clicks.