Size of .PST vs. size of actual mails

[Ponch]

I recently moved 70Meg of mails to a purposely created pst (Outlook 2010). Those are a big amount of small mails (typically 3kb) in about 15 sub-folders, so the info "about" the mail might weight more compared to the mail itself, OK, but still... ... The bastard was 350MB big, this is exactly 5 times the size of the mails as shown by Outlook! Then I thought "of course... a non unicode capable pst will surely be smaller". So I moved those mails to a new pst. The bastard was still 255Meg. After compacting (a new pst needs compacting? It doesn't cost a penny to try), it's down to 220Meg.

My question is: is this normal or is this Microsoft helping hardware manufacturers with Outlook 2010?

[tain]

In Thunderbird you have to "compact" or "expunge" to actually delete items instead of leaving them hidden/recoverable. Does Outlook have similar functionality?

[jaclaz]

Ponch, how exactly did you "move" those e-mails?

jaclaz

[Ponch]

I moved (drag & drop) 6 folders ("2012_06" to "2012_12") straight inside a new "2012" folder in the new pst. I did them one by one because I didn't know how long it would take and I didn't want to lock my outlook for more than 5 minutes at a time (the Exchange server is not on this location). But it went quite quickly. Then from the 2nd to the "non unicode" pst, I did it in one go.

Now Outlook shows the "Total Size" inside the pst as being 165Meg. This is ridiculous as I moved them following a warning that the mailbox had just passed 150Meg (so I moved about half the mailbox and Outlook was then seeing 80Meg remaining, now it's grown just a bit more).

Tain, Yes, when you empty a pst, you can compact it, but this is not my case. I don't want to delete items, I sort of filled a new bag which should be the size of what's in it.

[tain]

Prior to compacting/expunging, I could see how it would report different numbers if different routines are doing the math.

[jaclaz]

Well, how big are the actual .pst files on the filesystem?

AFAIK, the difference between the "normal" format and the "unicode" one is in the addresses, that are 64 bit instead of 32 ("ealrier" vs. 2003/2007):

http://en.wikipedia.org/wiki/Personal_Storage_Table#Formats_and_size

I don't think that there are much differences between 2003/2007 and 2010

jaclaz

[Ponch]

The pst is now on a network drive and is still 220MB (the other one I deleted). In there outlook sees 165Meg of mails. I could try reimporting them in the mailbox to see if it's back to the original 70Meg but I don't see what to do next in any case.

Update: Tests are not conclusive. even worse I would say.

I tried with one folder containing 1681 mails, Outlook says it's 7.9 meg, i make a new (non unicode) pst and copy the folder to it.

... Outlook now sees 12.7 megs of mail and the file is now 14.7Meg.

I move the folder back to the same mailbox (at an other place)

... Outlook now says it contains 4.1 meg. (still same 1681 mails )

I compact the now empty pst which goes back to ~750k and copy the folder (4.1 meg) back to it.

...Outlook now sees 12.8Meg of mail and the file is 16.2 Meg.

I create a new (non unicode) pst and move my folder from the mailbox (4.1 meg) to it.

.. Outlook now sees 16.2 Meg in it and the file is 18.1Meg. There is nothing to understand here.

Edited January 10, 2014 by Ponch