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Convert Mozilla Thunderbird MSF to PST

Written By Aswin Vijayan
Mack John
Approved By Mack John  
Published On January 19th, 2024
Reading Time 5 Minutes Reading

For transferring data from Mozilla Thunderbird MSF to Outlook; first of all what a user needs to understand, is the file formats that are being supported by these respective mailing platforms. The file formats in which data is stored happen to the most primary concerns while any user initiates any type of conversion from 1 particular email client to some other. If a user is using some email client that uses MBOX or MSF file formats and wish to make a switch over to Outlook, then MBOX / MSF to PST conversion is needed.

About PST Format

PST stands for Personal Storage Table. These personal folder files belong to Outlook. These data files store users’ mailbox account’s data consisting of email folders along with other items, like contacts, attachments, appointments, and much more.

About MSF Format

MSF stands for Mail Summary File. These MSF files are principally linked with Mozilla Thunderbird This email client stores content of every mailbox folder in 2 file types, as follows:

  1. Files with no extension: These are mail-storage files that have MBOX format. Though these files are created without any extension they are MBOX files consisting of email messages that represent a mailbox folder in Mozilla Thunderbird email client.
  2. Files with .msf extension: These are index MSF files or the Mail-Summary Files that are assigned to every mailing folder in Mozilla Thunderbird’s profile containing message summaries of those emails that are stored inside their corresponding MBOX files.

Why Export Thunderbird MSF to PST?

Microsoft Outlook email application is one of the most popular email clients that stores users’ emails as well as personal email data in personal folders i.e. the files with PST file format or Personal Storage Table. Even though Mozilla Thunderbird is surely a free & open source email platform, still it is lacking much functionality, which is found in MS Outlook. To be precise, Mozilla Thunderbird lacks personal data storage management. So, all-in-all, Thunderbird can’t be taken as a complete desktop-email-management-program. On the other hand, Outlook has it all to make it a complete end-to-end email management program. This is the reason why a good number of users look for the switchover and thus intend to export MSF to PST.

Can MSF Files Be Opened in Outlook?

The answer is NO! Converting the mailbox of MSF to PST is needed instead. There are two ways for it:

  1. Manual Way
  2. Using Some Professional Tool

Note: MSF files are the index files. They only store summary of emails and do not contain any email message. But since its linked with Thunderbird, people confuse it with mailbox files. SO, do note that to access Thunderbird email messages in Outlook, you must convert the MBOX file and not the MSF files.

Manual Way to Convert Mozilla Thunderbird MSF to PST

  • Import/export tools add-on is needed for this conversion
  • Run Mozilla Thunderbird
  • Open folder from which messages need to be exported from
  • Now, select emails
  • Then, right-click on those emails that are selected
  • And then Click the option of “Save As”
  • Now, choose file type, EML
  • After that, save selected emails in the destination folder
  • And then click on “Select folder”
  • Run Outlook program
  • Form new folder to store those converted messages
  • Enter some name
  • Click “OK”
  • Select all those emails that are exported from Mozilla Thunderbird
  • Drag all these emails to the new folder in Outlook
  • After successful completion of this import process, user can view all of those emails.

Manual Method’s Drawback

In the above stated procedure, the files were not converted to PST, but into anothe file format that Outlook supports. There are chances of

  • Data loss risk
  • Risk of losing message formatting
  • Risk of header-modification
  • Lengthy process to drag & drop every mail
  • Great deal of effort on users end
  • Risk of emails losing their SMTP headers
  • Only helpful with a few emails

Using Professional Tool to Convert MSF to PST

For overcoming the issues faced while using manual ways to export Thunderbird MSF to PST, a commercial solution can be used effectively to get efficient results. As an alternative, one can use MBOX to Outlook Converter, which is one of the most recommended third-party tools for converting Thunderbird mailboxes.


To export MSF to PST one should have the corresponding MBOX file that they need to import in PST file format. The reason behind this is that the MSF file is an Index file only so it does not contain any emails. Thus, one has to import the corresponding MBOX file to PST file format. The tool would ensure the following:

  • Accuracy
  • Speedy conversion
  • No data loss
  • No loss of metadata during conversion
  • Retention of exact metadata even after conversion
  • Message preview facility
  • Bulk conversion

For more information, you can refer to


The manual way is time-consuming unlike its commercial alternative, which helps users to easily convert Thunderbird MSF to PST. This saves users’ time and effort, and at the same time, assures complete conversion in bulk with data security. The above write up will help you to convert .msf to Outlook with easy methods.