I'm surprised you haven't had problems much longer. With POP, you have a timing issue, as Thunderbird is unaware of what goes on with the online account, other than what it retrieves. Each copy updates its own popstate.dat file, not aware that other copies of Thunderbird are also downloading. Switching to IMAP would eliminate that problem.

I'm surprised you haven't had problems much longer. With POP, you have a timing issue, as Thunderbird is unaware of what goes on with the online account, other than what it retrieves. Each copy updates its own popstate.dat file, not aware that other copies of Thunderbird are also downloading. Switching to IMAP would eliminate that problem.

Thank you so much. Is there anything specific that would have to be changed along with changing to IMAP? I feel there was some complication with IMAP years back when this was all set up, hence whey we went with POP but I can't exactly remember what the issue was.

Well, the benefit of IMAP is that all messages are kept online unless deleted. That ensures that all employees see all of them. IMAP is the direction of the future and this allows you and others to see the messages, whether at work, at home, or via your phone. This lets your business always have access. This does require creating new accounts on each PC. That is, you cannot convert POP to IMAP, although you can have both on the same computer during the transition. The risk factor for IMAP is that you are dependent on the email host to do periodic backups, as you are relying on the server to always be up. That is generally not a concern, but since you're in business, It may be worthwhile to gain confirmation from your email provider of their backup policy.

Sorry for all the questions, but I went to set up an IMAP account this morning, and ran into the following issue, after entering all credentials, when pressing "done" a popup says: "Error Creating Account, Incoming Server already exists"

I followed a walkthrough on switching from a POP to IMAP, https://support.mozilla.org/en-US/kb/switch-pop-imap-account, and feel like I completed all the steps. I have even completely removed the old POP account, thinking that might have helped, but still getting same error.

Please start over and omit the password. I have found that is often the trick to do that. And do review to ensure old account is removed, although that is not a prerequisite for using IMAP.

That worked, thank you. One final question, if someone opens an email on a different machine, I still get it on mine, but it is not appearing as "new" as in, it shows it has already been opened. Is there a way to have messages appear to be unread on all machines, until that specific user opens it?

To my knowledge, that isn't possible, since that setting comes from the server. I'm pleased all worked well. If certain employees handle specific account/users, you might want to consider setting up filters to automatically copy messages into workfolders and ask employees to do mail from the workfolder and not the inbox. That would ensure the designated employee could focus on assigned clients. Just a thought...