Was an Office 2010 user, but had to move to a new computer and 2010 was no longer available for download, so I installed Office 2021. On previous machine, Outlook had all 5 of my email addresses living happily together in a single .pst file - no problems. Everything looked and worked just as I needed. I exported this pst file thinking it would import and merge into Outlook 21, but obviously not. What I have now is 1 profile, (named "test", which I would also like to change) but with 5 different .ost files, and 5 different email addresses listed in the navigation pane, all with their own inbox and folder structure. I have not found any way to re-combine all this into a single .ost / .pst equivalent.
I have owned and been involved in multiple businesses and had these email addresses a long time, so I am talkiing about tens of thousands of emails and 8GB worth of data. Manual intervention is not realistic.
Thanks for any help, in advance!

Might need to install Outlook Classic and disable New Outlook.

Please see this Microsoft Support article and reply with exactly what version of Outlook you are using.

What version of Outlook do I have? - Microsoft Support

I have Classic Outlook, "Microsoft Office LTSC Professional Plus 2021".

1 - Is this your question on Microsoft Q&A or just a very similar situation?

Outlook 2021; 4 Pop Email accounts share 1 Data/pst file. - Microsoft Q&A

2 - My guess would be that your 2010 was using POP3 for all the accounts and was configured to use the same PST. But when you setup the accounts in 2021 they were added as IMAP, which can not share the same OST. Before we continue, please confirm by doing File -> Account Information/Settings -> Account Settings and look at the "EMail" tab, "Type" column. What do you see?

3 - 8GB worth of data

To get access to all the mail in the 2010 PST you just need to "Open" it. This will add it to your current profile as a top level folder and you should be able to access everything in it.
Open and close Outlook Data Files (.pst) - Microsoft Support

4 - profile, (named "test", which I would also like to change)

https://www.extendoffice.com/documen...file-name.html

1) Wow, just a VERY similar question, but no that is not me. I've only been at this for about 3 weeks.
2) Yes, all but the gmail accounts were POP/SMTP on the old PC/Outlook setup. All are IMAP/SMTP on this new, Outlook 2021 install.
3) I wondered about that, and thought that is how I should start on initial install, but the new install forced me to create a profile, and forced me to setup an initial email address. There was no way to bypass it that I could find. So then I assumed I would have to setup each of my other email accounts, which I did.
I'll be happy to open it and hope it adds the top level folder as you suggest, but I am still after this from my original question-
"5 different email addresses listed in the navigation pane, all with their own inbox and folder structure." how do I get everything consolidated? (In folder view, don't really care about the behind the scenes file/database structure, *.ost, *.pst).
thanks

You will have to remove the 5 email accounts from your profile and add them back as POPs all using the same, original PST file. Or, you can create a whole new Profile and add them from scratch as POPs using the same, original PST file.

The process is fairly straight forward but can get complicated depending on your email providers requirements for using POP vs IMAP.

What are the Domain Names (the part after the "@") for your 5 accounts? (Do NOT reply with your full email address).

If any are custom domain names, then who is the email provider company?

@frontier.com (taken over by Yahoo a year ago, causing MASSIVE headaches. Lost access to several other email accounts in that fiasco). They require using one-time passcode/password stuff that is very finicky.
@mediacombb.net
@gmail.com

I let Outlook do the setup on these accounts 'automatically' and they all came in as POP this time...

>> they all came in as POP this time...

I was not expecting that.

Are they all using the same, original PST file? i.e. You only have one top level folder and they are all under that folder?

Do you still have all of your original Contacts and Calendar events?

My original 2010 structure was:
>Outlook Data File
>Inbox, Drafts, Sent, Deleted, Junk, Outbox, etc...
All in one .pst, which I exported, weeks ago.

In setting up 2021 it forced me to create a profile, and to setup an initial email account, which was one of the @frontier.com. I could find no way around this. I then added my other emails using the same Outlook automatic method, and imported my .pst file. I wound up with a 2021 folder structure of:

>emailaddress@frontier.com
>Inbox, Draft, Sent, Deleted, etc...

>2ndemailaddress@frontier.com
>Inbox, Draft, Sent, Deleted, etc...

>3rdemailaddress@mediacombb.net
>Inbox, Draft, Sent, Deleted, etc...
repeated 2 more times, EACH OF THESE EMAILS IN ITS OWN *.ost FILE. I don't find any new *.pst file.

My calendar / notifications / events are working as expected. My contacts are present, but separated into weird groupings. (They also don't auto fill when I start typing one, but that is probably just a setting?) Another issue is that because I have had to use email, my original pst file is weeks out of date, with all the newer stuff only contained in the new ost files. :-(

I forgot to be clear that on 2010 ALL emails (regardless of which of my email addresses it was sent to) came to the one and only inbox, or were sorted to sub-folders by rules. That is what I would like to get back to on 2021.

Because you are using POP, which removes emails from the server once they are downloaded, this is going to get very messy.

Before you start - Make a backup of the original PST you brought over from your old PC and put it someplace outside the normal Outlook directories. e.g. "C:\OlkBackup".

Create a new, no email Profile. Name it something like "Consolidated". Change your settings to "Prompt for a profile to be used".
How to use Outlook 2016, 2019, 2021, and Office 365 without an associated Email Account - CompanionLink Support

In Outlook, using the Consolidated Profile, start adding your POP accounts. During setup for all of them, tell it to use the same, original PST you brought over from the old PC. Follow these instructions. NOTE - If it doesn't let you get to the "Advanced Setup" screen and tries to setup the account automatically you will have to use the "Invalid Password" trick.
Manually add POP or IMAP accounts to Outlook | Slipstick Systems

Once you get all the POP accounts setup in the Consolidate Profile - Import the emails from each of the separate PSTs that were created during your first try. Be sure to NOT import duplicates.
Import email, contacts, and calendar from an Outlook .pst file - Microsoft Support

If it goes sideways - Just stop and come back here. Do NOT delete any files or Profiles.

Once you have the Consolidated Profile finished and everything is working the way you want - come back and we'll go over deleting all the leftovers.

OK, but isn't there just a pill I can take to make it all better?
Much going on for a few days, and I'll have to dedicate some time to this. I WILL post back on any progress.
Thank you again!