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How do I keep deleted emails from disappearing forever using second computer on Imap

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Thunderbird was getting very slow so I deleted some emails out of my archive folder on computer (A). I later found that this made the same emails also disappear from my work storage folders I had moved the same emails into from my inbox. I have a second computer (B) and the missing emails titles still show up in the folders on that system but not the actual emails because I won't let it connect to the internet. I expect that once I let it connect to the net the second computer (B) will update thunderbird to match the first one (A). The missing emails are still there when I log directly into gmail. My gmail account are all imap. How can I fix this? Someone told me to make an offline folder on computer (B) and move the email to it so they won't be deleted off the server when I reconnect computer (B) to the net. I can't figure out how to make an offline folder and searching didn't help. What should I do to keep these emails? It's been over 90 days and I need to use computer (B) again. I attached a screenshot of Thunderbird in computer (A) I'm on 68.6.0 (32bit) If someone can help me I will gladly make a donation. Thank you! Art

Thunderbird was getting very slow so I deleted some emails out of my archive folder on computer (A). I later found that this made the same emails also disappear from my work storage folders I had moved the same emails into from my inbox. I have a second computer (B) and the missing emails titles still show up in the folders on that system but not the actual emails because I won't let it connect to the internet. I expect that once I let it connect to the net the second computer (B) will update thunderbird to match the first one (A). The missing emails are still there when I log directly into gmail. My gmail account are all imap. How can I fix this? Someone told me to make an offline folder on computer (B) and move the email to it so they won't be deleted off the server when I reconnect computer (B) to the net. I can't figure out how to make an offline folder and searching didn't help. What should I do to keep these emails? It's been over 90 days and I need to use computer (B) again. I attached a screenshot of Thunderbird in computer (A) I'm on 68.6.0 (32bit) If someone can help me I will gladly make a donation. Thank you! Art
Attached screenshots

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IMAP mail accounts store emails on the server (same place as you logging on to webmail account via a browser). Imap account folders are also on the server and those imap folders synchronise with server folders to only show what is currently on the server. If you delete an email from an imap account folder, it is deleted off the server. This means if you view the emails on the server via another imap account on another computer, that imap account will get updated to show what is on server. So emails that were deleted off the server via another imap account will get deleted from all imap accounts when they connect/synchronise with server. This is not a Thunderbird quirk, it is how all imap mail accounts work. They show a virtual view of the server.

If you want to delete emails off the server, maybe to release space and increase quota, you need to get copies in your 'Local Folders' mail account. The 'Local Folders' mail account does not connect to any server and those emails are stored in Thunderbird profile folders.

However, you do want to make sure you are copying full copies of emails and not just headers.

Emails in imap folders may be full downloaded or just headers. When you select to read an email, if only headers were downloaded, then thunderbird connects to server to download a copy which is stored in a temp file to faciltate viewing. Not everyone wants full copies downloaded as it may use up too much space on computer.

This is where you choose whether to synchronise and download full copies or headers and it can be done on a by folder basis.

  • Right click on imap mail account name in Folder Pane and select 'settings'

This opens the 'Account settings' window.

  • Select 'Synchronisation & Storage'

Please read info at the following link:


Once you are sure you have settings to 'Keep messages for this account on this computer' and all the relevant folders are definately selected by checking the 'Advanced' button, you can choose to go into 'Offline' mode to get a current up to date full downloaded copies of emails into Thunderbird.

  • Menu icon > File > Offline > Download/Sync now
  • choose to download 'Mail messages' and any other required. Also select to 'Work offline once downloaded....'
  • click on 'OK'

Info is displayed in the bottom Status bar. Once offline the 'two blue screen icon' in bottom Status bar will become 'two black screen icon.

In offline mode:

  • Create the necessary folders in the 'Local Folders' mail account.
  • Highlight batches of emails in imap folders.
  • Right click on highlighted emails and use 'Copy to' and choose the relevant folder in 'Local Folders' mail account.
  • Repeat as required.

If you can read those emails in offline mode in the 'Local Folders' mail account then you have successfully got copies. I strongly advise you use 'Copy to' option just in case something goes wrong, then you will still have the original in the imap folder and can repeat.

Once you have emails in 'Local Folders' you can go back into 'Online' mode by clicking on the 'two black screen icon'.

Using offline mode to get copies of large numbers of emails into Local Folders is a better option, as it it prevents all imap folders from synchronsing with server whilst you are copying a lot of emails from those imap folders.

Then you can delete emails from imap folders knowing you have copies stored in Local Folders mail account.

If this is a gmail account: Gmail stores all emails both sent and received in the 'All Mail' folder. You see them in other folders because gmail sets labels to faciliate a more meaningful view. Please make sure your deleted emails actually go into the gmail Trash folder. Otherwise you are only deleting labels and gmail will archive the emails in the 'All Mail' folder rather than delete them from the 'All Mail' folder. So you are not reducing your quota if they are not properly deleted.

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As a heads up: If you have a Pop mail account, then the folders do not synchronise with server. Pop accounts can only access server Inbox and download copies , those emails are stored in Thunderbird. You would need to ensure Account Settings are set to leave copies of messages on server otherwise they would auto get removed from server. Same occurs if you have a phone that is set up as Pop.

However, you may also have a setting to delete emails off server when you delete them in Pop account. So if another account on another device is set up as Imap, it will also see those 'deleted' emails disappear because they were removed off server. Sometimes, people experience emails disappearing from an imap account and do not realise they have a phone set up as pop which is deleting emails off server.

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Toad-Hall That was helpful. I realized that the deleted emails bodys didn't exist anymore. I was just seeing the headers. I donated to Thunderbird. Thank you, Art