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Purge emails from disk?

  • 4 replies
  • 1 has this problem
  • 9 views
  • Last reply by Wayne Mery

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I marked an email as "Junk" and it said I can purge deleted files from disk and save 3.5GB. However, I don't have any emails in my deleted folder?

I marked an email as "Junk" and it said I can purge deleted files from disk and save 3.5GB. However, I don't have any emails in my deleted folder?

Chosen solution

Just to be clear - and believe me there are alot of people who appear to be confused or worried about the wording in this 'purge emails from disk' pop up, so you are not alone.

It is not talking about the deleted emails that may be displaying in the the 'Trash/Deleted' folder.

The pop up message is appearing because you have a setting that is asking you compact when it will save you x amount of space. You are seeing it because you have reached the threshold that is set.

  • Menu app icon > Options
  • select 'General'
  • scroll down to the bottom to locate 'Disc Space' section.

To stop getting the popup:

  • uncheck the checkbox, (so not selected) 'compact all folders when it will save over x mb in total'

To allow popup to remind you to compact all folder

  • Select the checkbox: 'compact all folders when it will save over x mb in total'


Just so you, or indeed anyone else who reads this, really understands what is occurring and that you realise you could be increasing the risk of ending up with a corrupted file if you do not compact your folders on a regular basis, here is some information that should help you to understand what is going on.

Emails are stored in mbox files. An mbox file is a simple text document. So lets discuss the Inbox. As you download emails they are written to that one single text document, one after the other, so the oldest will be at the top. If you imagine it like one email is a paragraph, then you can understand there is a lot of paragraphs in that one single document.

When you delete or move an email, it looks like it has gone from the original folder eg: Inbox and reappears in the appropriate folder eg: Junk, Trash or another folder used for organising emails.

However, in reality, the original email is still in the 'Inbox'; it gets 'marked as deleted' and hidden from view, so to use the paragraph example, that paragraph gets the red pen treatment as a strikethough, but the text remains. After a while, the one single document will contain more deleted or moved emails than ones you keep in the Inbox. So using the paragraph example, you can now easily understand that the document looks a mess and is now hundreds of pages in length, yet only has a few emails/paragraphs you want to keep in that one single text document. Needless to say, it is also a lot bigger than it needs to be because of all the stuff you have either moved or do not want anyway.

Compacting means getting rid of all the stuff you have moved or deleted; purging - so the file becomes smaller, so uses less space, less memory to open, speeds up handling of file and is less likely to have corruption occuring.

If you never compact/purge from disk, then you need to understand you could end up with a file that might not be able to be opened very easily using a text editor program should you ever need to recover emails. You are increasing the risk of losing everything contained in that file.

So it is a good idea to allow auto compacting to occur. Alternatively, you can manually compact individual folders. right click on folder in Folder Pane and select 'compact'. The folders that usually require this the most are 'Inbox', 'Drafts' and 'Junk'.

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Chosen Solution

Just to be clear - and believe me there are alot of people who appear to be confused or worried about the wording in this 'purge emails from disk' pop up, so you are not alone.

It is not talking about the deleted emails that may be displaying in the the 'Trash/Deleted' folder.

The pop up message is appearing because you have a setting that is asking you compact when it will save you x amount of space. You are seeing it because you have reached the threshold that is set.

  • Menu app icon > Options
  • select 'General'
  • scroll down to the bottom to locate 'Disc Space' section.

To stop getting the popup:

  • uncheck the checkbox, (so not selected) 'compact all folders when it will save over x mb in total'

To allow popup to remind you to compact all folder

  • Select the checkbox: 'compact all folders when it will save over x mb in total'


Just so you, or indeed anyone else who reads this, really understands what is occurring and that you realise you could be increasing the risk of ending up with a corrupted file if you do not compact your folders on a regular basis, here is some information that should help you to understand what is going on.

Emails are stored in mbox files. An mbox file is a simple text document. So lets discuss the Inbox. As you download emails they are written to that one single text document, one after the other, so the oldest will be at the top. If you imagine it like one email is a paragraph, then you can understand there is a lot of paragraphs in that one single document.

When you delete or move an email, it looks like it has gone from the original folder eg: Inbox and reappears in the appropriate folder eg: Junk, Trash or another folder used for organising emails.

However, in reality, the original email is still in the 'Inbox'; it gets 'marked as deleted' and hidden from view, so to use the paragraph example, that paragraph gets the red pen treatment as a strikethough, but the text remains. After a while, the one single document will contain more deleted or moved emails than ones you keep in the Inbox. So using the paragraph example, you can now easily understand that the document looks a mess and is now hundreds of pages in length, yet only has a few emails/paragraphs you want to keep in that one single text document. Needless to say, it is also a lot bigger than it needs to be because of all the stuff you have either moved or do not want anyway.

Compacting means getting rid of all the stuff you have moved or deleted; purging - so the file becomes smaller, so uses less space, less memory to open, speeds up handling of file and is less likely to have corruption occuring.

If you never compact/purge from disk, then you need to understand you could end up with a file that might not be able to be opened very easily using a text editor program should you ever need to recover emails. You are increasing the risk of losing everything contained in that file.

So it is a good idea to allow auto compacting to occur. Alternatively, you can manually compact individual folders. right click on folder in Folder Pane and select 'compact'. The folders that usually require this the most are 'Inbox', 'Drafts' and 'Junk'.

Modified by Toad-Hall

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https://support.mozilla.org/en-US/kb/compacting-folders describes what this is about.

Is there anything unclear there?

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The explanation is now understandable - but I think the original message about purging emails is not - it needs modifying

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Sorry, yes it is confusing. Thanks for pointing this out.

Version 91 comes out in several weeks, in which the language of the compact dialog has been greatly improved. When you install version 91, if compact causes problems, please create a new support topic.