How To Deal with ‘Import MBOX Greyed Out-File’ Issue?

Megha Sharma
Megha Sharma linkedin | Updated On - November 18, 2022 |

Read time 4 minutes

Sometimes, users of MBOX email clients like Mozilla Thunderbird face some issues with MBOX files, disrupting email communication. And the MBOX greyed out file issue is the prominent one among all issues nowadays. We will have a complete discussion of this MBOX file issue.

What is The “Import MBOX Greyed Out-File Issue”?

Mozilla Thunderbird is a well-known desktop email client which stores emails in in MBOX/MBX format. And, yes MBOX files are not at all devoid of corruption and issues. One of the issues faced by many users is “MBOX Greyed Out-File Issue,” in which the user is unable to import MBOX folder in Thunderbird application. This greyed out situation of the MBOX file causes difficulties in accessing emails.

The error usually comes with the following error message:
Cannot Import messages: "The Import Messages from a Directory" is Light Grey.

The causes for this error can be corrupted, damaged or broken MBOX files, bugs infection in the email client, application not updated, software conflicts, missing files in directory, etc.

Some Basic Solutions for “Import MBOX Greyed Out-File” Issue

Here, we are providing you some of the solutions which you can perform immediately after getting the error “Import MBOX Greyed Out-File” issue.

  • Close the Thunderbird application, open again and try importing the MBOX file.
  • Check the file structure of the MBOX file, especially the header.
  • Try updating the Thunderbird application to the latest available version.
  • Disable add-ons and other software applications causing conflicts.
Try a Professional MBOX Viewer Tool

If you want to view the MBOX file data, then you can go for an efficient MBOX Viewer tool, which can display your MBOX files. Kernel MBOX Viewer is a free viewer tool that can read, open and view MBOX files data. It supports more than 20 MBOX email clients including Mozilla Thunderbird email client.

Functions and Benefits Offered by Kernel MBOX Viewer
  • Absolutely free for all
  • Read & open MBOX file emails
  • No file-size restrictions for MBOX files
  • Displays MBOX emails along with meta-properties
  • User-friendly and interactive Graphic User Interface
  • Maintains the structure of the MBOX file emails
  • Saves retrieved MBOX emails list in the HTML format
  • Supports about 20 email clients, including Eudora, Thunderbird, AppleMail, SeaMonkey, etc.

To get a complete understanding about this tool, here are the the main steps involved in the working of the free Kernel MBOX Viewer tool.

  1. Download the tool from and install it in your system.
  2. On the welcome screen, select the MBOX email client.MBOX Viewer tool Home Screen
  3. Now, add the MBOX files using the relevant button.Add MBOX files
  4. The mailbox data including all mailbox folders will be displayed. You can click on any MBOX mailbox folder to view the detailed preview.View MBOX file

Thus, with this tool, it is easy to read, open, and view the MBOX files without any MBOX email client.


Import MBOX Greyed Out-File’ issue restricts MBOX email client users from importing MBOX files into the Thunderbird application. Some minor manual solutions can help to combat this issue if the problem is not significant. Otherwise, trying a professional MBOX viewer tool can be the ultimate solution.

Kernel for MBOX to PST