This is how IMAP works. Are you sure your devices are really using POP?

IMAP mail accounts see a remote view of the server. All emails are stored on the server. You can synchronise folders to get a copy into Thunderbird, but those folders synchronise with server. in effect, the fodlers you see in Thunderbird are the same ones you see via webmail or any other device accessing by these two methods. Any email you delete via Thunderbird or webmail will delete off the server and so will not be shown in either Thunderbird or webmail or any device accessing the server. So if Laptop and phone are accessing the server using imap or webmail, then a deletion done via Thunderbird, webmail or phone will delete off server and then delete from all other devices when they synchronise with server.

POP mail accounts can only access server Inbox and usually download to Thunderbird and them get auto deleted from the server. Pop mail accounts store emails in your Thunderbird profile . Folders created in Thunderbird are only in thunderbird. They are NOT synchronising folders like imap. So, you can delete off server and stilll see emails in pop mail account. However, if you have set up your Thunderbird 'Account Settings' > 'Server Settings' to 'Leave messages on server', then that email will still be visible via webmail or any other device accessing that server.

If you also have Account Settings set on either of the following:

• selected :'Leave messages on server'

and also selected....

• selected 'For at most xx days'

then any downloaded email will be keep on server for a period of time as set by number of days and it will then be auto deleted off server, but will still be visible in thunderbird.

• selected : 'Until I delete them'

then any message you delete in Thunderbird will get deleted off the server. If message is deleted off server then it will not be available to be seen either by webmail or via any other means that access the server via pop or imap.

Thanks for this. My main account name was created as POP on all 4 devices (2 laptops and 2 smartphones). My second account name was created on both laptops as IMAP. All emails are received into both account names in-boxes on all 4 devices. In the account settings for the main account name on both laptops I have checked the 'Leave messages on the Server' box. Did not have that option for the second account (IMAP). Just wondering if it's anything to do with what's been set up as POP and what for IMAP. Again, apologies if I've not been clear in my phraseology. Thanks,David.

POP on a smartphone? That seems to be rather unusual. POP generally leads to a persistent download to the device, and so eventually it would fill up you phone's precious flash memory. IMAP would, OTOH, selectively download as you open messages (and presumably discard older messages.)

I believe that email clients on smartphones don't use pure POP or IMAP. I've had devices that were supposedly IMAP but didn't delete from the server. I think they recognized that you might not want certain message cluttering your phone, but you wouldn't necessarily want to delete them permanently, so behaved more like a POP client, but didn't delete the server copy on download, and very likely "retired" the downloaded message after a period of time or when memory usage required it. However it also allowed me to browse folders on the server and thereby access older messages filed away in subfolders, hence behaving like IMAP.

Thank you for this. Should I re-create all my POP server settings as IMAP? Any pros and cons, please? Thx, David.

re : I have checked the 'Leave messages on the Server' box. Did not have that option for the second account (IMAP).

POP - checking the 'Leave messages on the Server' box option and none of the delete options, will stop any deletions from server via Thunderbird pop mail account. So you can see received emails via webmail or imap connection from another device as emails will still be on server. This will mean you will need to keep an eye on how much of your server quota you are using as nothing will be deleted via Thunderbird pop mail account. You can still delete emails from your pop mail account and they will not be deleted off server. POP mail account emails are stored in your Thunderbird Profile folder name. One benefit of leaving a copy on the server is that you can use it as a type of backup as it is a second copy of received emails.

In IMAP mail accounts the 'Leave messages on the Server' option is not available because all your emails are stored on the server. IMAP mail accounts just see a remote view of what is on the server. This means you can access those emails via Thunderbird imap mail account and via webmail account and via any other imap mail account. But anything you delete will be deleted off the server and therefore will be removed from any other imap view. These emails are only stored on the server; they are your only copy. You can get a copy into Thunderbird by synchronising folders for offline use, but any deletions willl still be removed from Thunderbird and the server.

Another benefit of imap - if you need to access via a new/another computer, it is easy to create new imap mail account and hook up to the emails held on the server.

It is worth remembering that if want to close the webmail account, you must get a copy of all emails on the server into Thunderbird (or another email client) because once closed, you will no longer get access to those emails held on server.

If you have too many emails on server and need to create space, but do not want to lose emails, then you can synchronise folders for offline use and in offline mode move emails into 'Local Folders'. Then delete copy off server.

If you need to use more than one device to access emails maybe because you use different computers in different locations, then I would suggest you use IMAP; you will also see emails you sent.

Both IMAP and POP mail accounts should get backed up and the copy stored externally eg: external hardrive, memory stick (needs to be large enough).

• http://kb.mozillazine.org/Profile_backup
• http://kb.mozillazine.org/IMAP_backup

Thanks, once again! So, please, should I delete/recreate email accounts on the 4 devices as all POP or all IMAP - or what?? Thx, David.

David it depends on what you want to achieve. As others have explained, if you set up the account with IMAP folders on all four devices they will be synchronised with each other. Consequently if you delete an item from the Inbox on one, it will disappear from the Inboxes on the others too. That's how IMAP works. If you set up the account with IMAP folders on some devices and POP folders on others -- assuming that your email provider allows this -- then the behaviour on deletion is likely to be erratic and unpredictable, as you have discovered. Personally I treat my IMAP Inbox as the place for unread mail and for read mail that I need to deal with soon. When I have read it and dealt with it, I either delete it or move it to one of several other folders. The other IMAP folders I can synchronise across devices or not as I wish. That's just my way of working; you're obviously using your Inbox in a different way to me. No one on this forum can advise you whether or not to make your folders IMAP or POP. All we can do is to help you understand how the technology works, what it can do and what it can't. You then have to decide what you want to achieve and what is the best way to use the technology for your own purposes.

If you want to be able to delete emails from eg: Thunderbird, but still be able to view them on the server/webmail, then you will need to use POP mail account and make sure the Account Settings have the 'Leave message on server' selected and do not select any of the delete off server options. see image below. Then if another computer/phone logs on to see webmail, the incoming emails should still be available. POP mail accounts download and store emails in Thunderbird profile on your computer completely separate from what is on the server. All sent emails will only be available in Thunderbird. They are not stored on server. If you create various folders in Thunderbird pop mail account to organise emails, then they are only on your computer in the Thunderbird Profile.

If you want all your 'Sent' emails to be visible on other devices then they would need to be stored on the server, so you would need to use IMAP.

IMAP relies upon you understanding that emails are stored on server, which you can see via webmail. Any device accessing via imap will get a view of what is currently on the server at time of accessing. Any deletions will get deleted off server and therefore, will get deleted off any remote view accessing that server when it synchronises its view.. You have to treat it as if there is only the one place where the emails are stored - on the server, but different ways of seeing the same folder. Folders are on the server, you subscribe to see a view of those folders. If you create a new folder then it will be added to the server folders. there is much synchronising going on between all your imap subscribed folders and the server.

So to determine what you should use depends upon what you want to achieve. Your initial question seemed to imply that you actually like using POP. So you need to make sure the POP mail leaves a copy on the server and does not delete. see image below then click on 'Disc Space' select 'don't delete any messages' select 'Always keep starred messages' click on OK.

Thanks to one and all for your replies and advice. I need to re-read all above and make sure I get my head round it all, then I'll decide how I need to proceed. On this basis, I'll say the problem is now solved. Thanks again! Best wishes, David.