pop3 to imap?

What will happen to the folder structure currently in place on the PC? Will this copy to ISP's mail server & then all other devices will have same look? The guy I'm doing this for can be rather picky at times, like when I finally pried XP out of his hands & moved him to Win7, one of his complaints was that all his desktop icons weren't arranged & in the same position on new computer!
I'm assuming I can duplicate my own profile on my computer, make the change & see where/how the chips fall, keeping my original pst file that I can always fall back on?

You really need to wrap your head around about what POP3 and IMAP is and isn't. Also, there's no mention of which version of Outlook your question involves so for the sake of this response, the presumption in all things mentioned is that this is either OL'2013/'2016 with a single POP3 account configured and one PST file in the Outlook profile

#1 - POP3 and IMAP are "protocols" used to access a given email account - each of which enables different functionality
#2 - Regardless of how an account is accessed by ANY email client - there is only ONE email account. Most ESPs allow the same email account to be accessed using <either> POP3 or IMAP but some like Gmail require that the method used to access the account is set at the server level.

#3 - To recap the article on protocol differences in the previous post
a) POP3 only allows a one-way one-time (per email client) "download" of items in the <Inbox>. Whether or not those items remain in the <Inbox> on the server depends on the setting for "Leave Messages on server" (applicable only to POP3). All other folders defined in the <Email Client> are "local" only to that device

b) IMAP enables a bi-directional "sync" of all "email" folders (that have been subscribed to in the <email client>). Translated, whatever is added/deleted in a folder on any device gets applied to the server (and vice versa). All other devices using IMAP to access this account will see the changes or in other words, all devices will see the same thing.

c) Contact/Calendar info is always "local" to given device regardless of whether POP3 or IMAP is used. If that info needs to be sync'd across multiple devices, then it needs to be stored/accessed using an account supporting the Exchange protocol (either Outlook.com or a hosted Exchange account). Having contact/calendar data anywhere else (i.e. Google contact/calender) requires a 3rd party Outlook addin.

How to share Outlook contact/calender data using POP3 and Imap accounts
http://www.contactgenie.info/how-to-share-contacts-pop-imap-accounts

4) just to be very clear - you don't "change" an account from POP3 to IMAP. You configure the same email account using the applicable protocol. Removing an POP3 email account does not remove the associated PST file from the Outlook profile, which in this scenario would also be the "default data file" for the profile which then in turn means that this PST file contains the "default" contact/calendar folders. That is important since if you configure the email account using IMAP in the same profile where the PST file exists - the IMAP folder tree will not have any contact/calendar folders. Or to address you question of what happens to the existing POP3 folder tree - answer: nothing, as in nothing gets copied to the server

You could create a new profile and then configure the account using IMAP at which point the IMAP folder tree will include contact/calend folders with the added description of "This Computer Only" (see other articles referenced in my original reply). You then would need to add the PST file associated with the POP account to this profile.

Once you have configured the IMAP account, you would need to "copy" the POP3 foilders to the IMAP account. I stress the use of the word "Copy" vs "Move" so that no source info is lost in the process should things go sideways for any reason during a "move". When you go though that process, strongly suggest that you set Outlook to work in "offline" mode until everything has been completed. When done, set Outlook to "online" mode and do a manual send/receive on the account to invoke the sync process for all the data

5) doesn't matter which computer you use to configure the IMAP account - once it's all done, any computer configured to use IMAP will see the same thing

6) make sure that there is sufficient capacity at the server level of the all the data that is going to be uploaded. Each ESP (email server provider) has their own limits.

7) if you plan to go thru the exercise just to see how things turn out for a user that is still actively using his POP3 account - just remember that all additions/changes that occur after you have copied the PST file, will not be reflected in the IMAP based folders on the server.

Yes, I am dealing with Outlook 2013 & a pst on that computer. The more I dig into this, I'm womndering if this isn't the answer to my situation, or if it is, there may be other considerations.
On his main computer at the office, his pst is just under 2 GB. He has quite a few subfolders, as well as contacts & calendar info on that computer, as well. Since devices have been set up for a whie, he's also got contacts on them, but little (if none at all) in the way of subfolders.
So if I just change the protocol on work computer to IMAP, is it necessary to copy folders back to server? His ultimate goal here is to just delete emails on one device, not everyone he has.
And this just in, his ISP, Logix, says they're geared more for POP3 accounts & have a 50 MB (yes, MB not GB) limit before they start charging 'storage fees'.
They do offer exchange hosted plans, too, but will need to wait till Monday to talk to them about that.

All that being said, what would be the easiest (& 'cleanest) way to manage duplicate emails across several deivices, keeping current contact & folder structure as is on each device, or is this even possible?

#1 - As stated - you don't "change" the protocol - you need to configure the account using IMAP - just for the sake of accuracy.

#2 - Re: "So if I just change the protocol on work computer to IMAP, is it necessary to copy folders back to server? His ultimate goal here is to just delete emails on one device, not everyone he has."

You've now got me completely confused about what the ultimate objective is in all of this unless in terms of how all the devices are configured and going to be used in all of this. So does he want all the devices to have all the sub-folders as well or is this a case of just wanting to share the <Inbox> across devices? Something is really not clear. Don't know what more info I can provide regarding how an account configured using and IMAP works. Email data in a PST file is "local only" and whereas the IMAP data is a mirror of what is stored on the server - neither of which deal with contact/calendar data

#3 - As for the ISP's 50mb limit - unless there is going to be some "extremely" tight control on the <Inbox> - first reaction is that question is could very well be very academic and moot depending on the volume of email rec'd - certainly wouldn't be an option if the intent is to share the content of sub-folders across devices. A hosted Exchange account would seem to be the far more prudent approach to follow making everything easier and simpler across the board - whether obtained from the ISP or directly from Microsoft (which would be my recommendation) but at the very least, if the decision is to go the ISP route - make sure you know what the EX account capacity limits are going in - the Logix website seems to have a serious lack of info for their EX offerings as compared to many others I've seen especially given a "50mb" limit before charging fees for a non-EX email account.

For point of reference -

Exchange Online
https://products.office.com/en-ca/exchange/try-or-buy-microsoft-exchange-business-email?siteID=SRi0yYDlqd0-B5MiHkpFBM92QZbiMURwCg

Basically, he'd like to delete emails from one device & have them gone from all devices.
I did warn him about the possibility of all of his devices having the same folder structure/look & from knowing him & confirming via phone call, this would not be what he was expecting.
If this isn't possible, he would probably be fine with that.

With all due respect, we're just going around in circles with this. As I mentioned in my 2nd reply - "You really need to wrap your head around about what POP3 and IMAP is and isn't." and there has been no shortage of info provided to that end. Am still not certain about what the ultimate objective is in all of this - there is something seriously missing from this description of requirements.

Re: "Basically, he'd like to delete emails from one device & have them gone from all devices."

Delete from where - the <Inbox> only or the folder tree as it exists under the POP account?

Going to try to recap this one more time at which point there isn't going to be much more I can add to this

#1 - Every device - whether PC or mobile has an <Email Client> where <email accounts> get configured using a specific "protocol" (POP3, Imap, Exchange ActiveSync etc)
#2 - What a given protocol can and can't do with an <email account> applies to all <email clients>
#3 - POP3 only deals with the <Inbox> folder <full stop>. The one option that is of importance with that protocol is where or not the <Inbox> items remain on the server after being accessed with a client using POP3. (see earlier descriptions of protocols)
#4 - If the data is not stored on the server, it can't be accessed by an email client regardless of device. Given the self-described 50mb limit, copying the data in the existing POP3 folder tree (local to the device where created) to the server and then accessing it via IMAP is a complete non-issue since there isn't sufficient capacity. The only choice is going to be a hosted Exchange account with all data copied to the server

Finally, how are all these other devices currently configured in terms of protocol used to access the email account? (default typically would be using IMAP. Given that the sub-folder data doesn't exist on the server - it wouldn't be available to those devices.

In any case, if things still aren't clear after this post along with all the info already provided - will have to leave this to someone else to better explain things.

I certainly appreciate your patience & wish I could award you extra points for that, haha!
In just looking at this on my own devices, my main computer (Dell Laptop,Win7, Outlook 2007) has email set up as POP3 client. For whatever reason, I had thought Apple devices defaulted to IMAP when setting up an email account, but looking at my iPhone 7 (email set up many iPhones ago), I see its a POP3, but yet if I set up same account on my iPad, it defaults to IMAP(?).
Personally, I really don't see why anyone would need email on much more than your phone & one computer, but that's just me!
If he really wants to do this, I'm going to tell him he's going to have to be fine with seeing entire inbox, just like it is on his work computer, on all his devices & steer him in the Exchange hosted direction.
And should he do that, I'm assuming best plan of attack would be to delete email accounts on all other devices, set up on main computer, copy inbox to server & once that computer is right, set up accounts on other devices. Does that sound like a plan?
Thanks, again!

Were it me in this scenario - I'd be a tad forceful in "strongly recommending" a hosted Exchange solution for all kinds of reasons ranging from a 50mb storage limit on the current account all the way up to saving money on what I perceive would be inevitable consulting fees down the line trying to get everything right (am only saying this "half-jokingly")

A hosted EX account solves all the problems since it deals with ALL email account folders (<Inbox>, secondary email folders, <Sent Items>, contacts, calendar etc etc) which will be accessible to all devices. Just need to copy all the local data currently on his computer to the corresponding EX folders and configure all devices to use Exchange/Exchange ActiveSync protocol.

I will suggest that, but he's got 20 or more sub folder & not sure if he had rules that send mail from certain people to specific folders, or not, but knowing him, that will be an issue!

not sure if he had rules that send mail from certain people to specific folders, or not, but knowing him, that will be an issue!

From OL menu --> File --> Manage Rules & Alerts --> Option tab --> import/export rules

BTW - issue would apply whether going from POP-->Imap or POP-->Exchange. Only 100% guarantee of absolutely no issues occurring is to keep things "as is" and not making any changes at all.