Using POP or IMAP

User Help for Mozilla Thunderbird
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Joined: February 21st, 2018, 4:45 am

Post Posted April 10th, 2019, 7:09 am

Hello Team,

I wanted to use Thunderbird to read messages offline.

I have my account logged on in three different devices.

Which option should i use to meet the below.

-Have consistency of mails both on online server and offline server.

-If I make changes on my online Server , e.g. delete an email online, it should not sync the effect/affect my offline messages.

-I would like to have all copies of my emails sent and received on all the three devices.


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Joined: July 30th, 2003, 5:06 pm

Post Posted April 10th, 2019, 7:40 am

FYI This forum is not run by or formally associated with Mozilla. We're an independent user community. The developers typically don't read threads in either our forums or the official forum (another user community).

I assume the three devices are desktops and/or laptops running Thunderbird, and none of them are smart phones or tablets. Smart phones and tablets typically only support email clients that use IMAP.

If you want to be able to read messages offline on any device, and don't want to deal with sync issues, you're better off with a POP account. In server settings check "leave messages on server", and don't check the nearby "for at most X days" and "until i delete them". If you have multiple POP accounts its possible to store the mail for all of the POP accounts in one account. See for more information.

Posts: 748
Joined: February 12th, 2005, 8:33 pm

Post Posted May 7th, 2019, 10:37 am

You have two irreconcilable requirements.

If you want to have all messages on your computer, even if you delete an email online, then follow Tanstaafl suggestion and set your account as POP.
As he said, if you keep messages for X days, you will be able to download them on all computers, but you will have the following limitations:
– If, on computer 1, you move some messages to different folders, they won't be moved on other computers. The only way to get the same "picture" would be to only move messages automatically with rules and to have the same rules on all your computers. That could work on Thunderbird (with lots of discipline), but it won't work on your telephone or tablet where you can't have message filters.
Messages that you send from one computer won't be accessible on any other.
There is no way around that because sent messages are stored in "Sent folders" and POP only downloads messages you received.

If you set IMAP, you will automatically have a perfect, consistent access to all your messages (received and sent) on all your computers, telephones, tablets, etc.. This is generally the setup I would highly recommend.
Here are a few tips to achieve most of what you want (the only downside later):
– In Account Properties, select "Synch and disk space", then click on "Save all messages on this computer, Synch all messages locally without age limit, and Never delete any message", so that you will have a complete copy offline.

The only of your requirement that is missing is that when you delete a message online (or on any of your computers), it will be deleted on all others. There are a few ways around it:

a. Don't worry and let everything on the server for ever and ever. With most providers, it's not an issue if you keep messages for ever.

b. Move older messages to archive folders.
If you want a faster connection (especially on a phone), create folders such as "Archive-Inbox" and "Archive-Sent" where you will transfer, say, messages that are more than 3 or 4 years old. It will make your Inbox smaller but your old messages will still be available everywhere if you ever need them.

c. If you need to purge some messages from your server (ex.: ISP tells you so), do the following on your main computer:
– Create "Archive-Inbox" and "Archive-Sent" under the Local Folders hierarchy
– Move older messages from Inbox to Archive-Inbox, and from Sent to Archive-Sent.
– Tip: Don't move 20000 messages at once; move a block (ex.: 1 year at a time) and stay connected overnight (depending on your connection speed) so that messages are transferred.
Once the transfer is done, these older messages won't be on your server and won't be accessible from your telephone and other computers, but they will be available from your main computer so they won't be lost forever.
Michel Gagnon
Montréal (Québec, Canada)

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