Well if they are still in gmail we can get them back to outlook. But of course they wouldnt be sorted into subfolders. If you had some sort of rules by which you sorted them ie if it was from a certain person it goes in this folder if it had xxx in the subject line it goes in that folder we could set those up to do it automatically for you.
As for the old outlook file we can certainly try but if it doesnt come right up every recovery process or utility that i know of will lose the folders as part of the recovery process so its not a lot of use to you.
If you had 30,000 emails in one folder it most likely did get corrupted. Outlook is designed to work with 500 mb of storage space. Above 2 gb microsoft flat out says its not supported and wont work. What you need to do is archive them. that puts the older ones into seperate pst data files where you can try to keep each of them well below 2 gb.
Here is about the only thing that you can try.
go to control panel / mail ( if its windows 7 it will be under family )
click on profiles
create a new profile
give it a name
tell it that you dont want to add any email accounts to avoid it downloading 30k gmails
check the box for prompt for profile on startup or to use the new profile when outlook starts
from the windows start menu search box
search for *.pst
You will need to set it to search in hidden and system folders. If that is not obvious to you how to do it i need to know what operating system you are using to tell you how.
locate the pst file that has most of your data. It will probably be the largest one and you can see how much over 2gb it is just to see.
copy it to my documents folder
open the outlook
You dont say what version you are using. In 2007 you would go to
file / data file management
click the add button its kind of on the top but not the very top of the window
browse to my documents and select the pst file that you copied
click ok etc
you should now have a second set of personal folders with all of your old data in it folders and all.
It may take awhile to be able to open them as outlook will have to reindex them all. That could easily take hours when its that large. But if it gives you an error when you try to add the file there is probably nothing that you can do to get the folders back and it would be easier to download them from gmail and sort them out again than to try to recover from the pst file and STILL have to sort them out again.