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append-only mode for IMAP synchronization (prevent server from deleting messages)

  • 2 replies
  • 0 have this problem
  • 8 views
  • Last reply by Marcin

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Hi. I'm looking for a way to block message removal by the server in the IMAP protocol - the "(server) append only mode" (it should be still possible to delete/move message from Thunderbird).

Why? I see 2 main use cases:

1. The (corporate) server has message retention set globally (e.g. to 1 year) which "cannot" be changed. Users might want to keep their "important" email longer (and in addition, keep it in the same folders as before, not using the folders copy in the "Local folders" space).

2. Due to the unexpected situation - a server error, fire in a data center, a ransom attack, malicious email provider - all the email (or some of them) are removed from the server. Thunder would sync with the server removing the messages from the synchronized folder on a computer (sure, backup is good, but for the "silent action" - e.g. part of the emails deleted (or encrypted), it might take too long to detect that problem and still have a valid backup).


The are some (not perfect) workarounds, including:

  • keeping old emails in the "Local folders" - two places to search (or many if you have a folder hierarchy with the automatic filtering)
  • a separate, local IMAP server to keep an "append only" copy of the message (e.g. isync, offiline imap), possibly to be used by Thunderbird (instead of the upstream IMAP server)
  • using POP3 (with its own downsides :) )


An obvious downside of the implementation in Thunderbird - which users of that feature have to be aware - is not doing any delete/move operations on the server (e.g. with the webclient or some other IMAP client). Nevertheless, to fulfill the aforementioned requirement it doesn't seem a high cost.

Questions: 1. Is it possible to achieve in Thunderbird itself? 2. Is there any API to help implement that as an extension? 3. Have you - by any chance - tried to implement that using the third party tools (e.g. a local IMAP server which is used by TB) and can recommend any solution? 4. (Bonus) Do you think it would be an useful addition to Thunderbird?

Marcin

Hi. I'm looking for a way to block message removal by the server in the IMAP protocol - the "(server) append only mode" (it should be still possible to delete/move message from Thunderbird). Why? I see 2 main use cases: 1. The (corporate) server has message retention set globally (e.g. to 1 year) which "cannot" be changed. Users might want to keep their "important" email longer (and in addition, keep it in the same folders as before, not using the folders copy in the "Local folders" space). 2. Due to the unexpected situation - a server error, fire in a data center, a ransom attack, malicious email provider - all the email (or some of them) are removed from the server. Thunder would sync with the server removing the messages from the synchronized folder on a computer (sure, backup is good, but for the "silent action" - e.g. part of the emails deleted (or encrypted), it might take too long to detect that problem and still have a valid backup). The are some (not perfect) workarounds, including: * keeping old emails in the "Local folders" - two places to search (or many if you have a folder hierarchy with the automatic filtering) *a separate, local IMAP server to keep an "append only" copy of the message (e.g. isync, offiline imap), possibly to be used by Thunderbird (instead of the upstream IMAP server) *using POP3 (with its own downsides :) ) An obvious downside of the implementation in Thunderbird - which users of that feature have to be aware - is not doing any delete/move operations on the server (e.g. with the webclient or some other IMAP client). Nevertheless, to fulfill the aforementioned requirement it doesn't seem a high cost. Questions: 1. Is it possible to achieve in Thunderbird itself? 2. Is there any API to help implement that as an extension? 3. Have you - by any chance - tried to implement that using the third party tools (e.g. a local IMAP server which is used by TB) and can recommend any solution? 4. (Bonus) Do you think it would be an useful addition to Thunderbird? Marcin

Modified by Matt

All Replies (2)

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I think you need to become familiar with the concept of the server being the canonical source of mail in the account in IMAP before going any further. I am not aware of a read only mode for IMAP servers, they might have them. But not in Thunderbird. Thunderbird implements what the server says it supports.

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Matt said

I think you need to become familiar with the concept of the server being the canonical source of mail in the account in IMAP before going any further. I am not aware of a read only mode for IMAP servers, they might have them. But not in Thunderbird. Thunderbird implements what the server says it supports.

Thanks Matt for your reply. I've been dealing with different corner cases with (mostly) corporate IMAP servers and as a person who has been using POP3 for years (with its obvious drawbacks), that brings some anxiety. I have seen that feature in OffilineIMAP, so it seems to be possible to achieve, however, using OfflineIMAP as a proxy for Thunderbird is some solution, but definitely generates also some other issues :-/.

I realize, it is very uncommon (however, definitely I'm not the only one ;-)), but I wanted to explore a topic.