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sasllcFlag for United States of America

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How to expand max Outlook 2016 file size?

Customer is using Outlook 2016.  The .pst is just under 2GB.  Today they get this error:

The Outlook data file C:\OutlookData\Outlook.pst has reached the maximum size.  To reduce the amount of data in this file, permanently delete some items that you no longer need.  You could also consider using the new Outlook data file (.pst) introduced with Outlook 2003 that provides great capacity for storing items and folders.

I don't understand why it is referring to pre-2003 since they are using 2016.  I guess it is possible that their .pst has been utilized over the years as they have updated Outlook, and maybe it originated long ago with a very old version.  I don't know if this is the case...just speculating.

In any case, I just want to be able to go way beyond 2GB, so I found info online indicating that I could simply change the max size parameter by going here in the registry:

To begin the process, click on the Start >> Run
After that, type regedit in the Open box and click on the OK button
Now, you need to expand My Computer option from the left pane. Then expand HKEY_CURRENT_USER
Next, you need to expand Software >> Policies
Then, expand Microsoft >> Office
After that, based on the versions, expand:
11.0 for MS Outlook
12.0 for MS Outlook 2007
14.0 for MS Outlook 2010
15.0 for MS Outlook 2013
16.0 for MS Outlook 2016
Then, simply expand Microsoft Outlook
Now, you need to click on the PST file and in the right pane, right-click on the MaxLargeFileSize
Here, you have to click on the Modify button and enter the value in the Value data box
At last, click on the OK button
In the same, a user can change the value in WarnLargeFileSize data also. You just need to right-click on it WarnLargeFileSize and follow steps from 8 to 10.

The problem is that  when I get down to step that says "simply expand Microsoft Outlook", there is nothing to expand.  If I click on 16.0 all it shows is a default REG-SZ parameter.  Below the 16.0 folder are subfolders such as Common and then Security and then Trusted Protocols etc., but I see nowhere to set MaxLargeFileSize.  I searched for this parameter in regedit but it found no matches.

The customer does not want me to archive.  They just want the .pst to keep growing, which sounds reasonable since it is only 2GB.  Any suggestions on how to best solve this size issue?  TIA
Avatar of J0rtIT
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Yes, you don't mention what is the version of the exchange server, is it online or onprem?

You don't expand it on the outlook side, you do that over the server's side.
Avatar of sasllc


This is not an exchange setup.  It is a standalone PC with it's .pst on the C: drive.  The version of Outlook 2016 they have is the one you pay for once and download and install on the local PC.
Yes, this has nothing to do with Exchange and even if it did, you make the adjustment on the pc.

HOWEVER, if it's warning you about a 2 GB PST then it's probably an ANSI based PST file rather a unicode PST.  Unfortunately, you cannot convert it.  You would have to create a new PST file (the default type should be Unicode these days) and copy the contents of the old one into the new one.  Or leave it as an "old email" PST and start new with the Unicode file.  Unicode files default limit is 50GB and that can be increased.
Avatar of sasllc


it sounds like the ideal method would be to create a new unicode PST file and copy it all over.  Better yet would be if the new filename could still be Outlook.pst where Outlook would not know the difference when I restart it, and it would just carry on with no more warnings and continue to expand the file.

If this is possible, then I need some details on how to do it.  Here are my questions at this point:

1) How should I create the new .pst file?

2) How should I copy the contents of the old one into the new one?

Details or examples are needed--so I don't mess up the customer's email.
Avatar of Lee W, MVP
Lee W, MVP
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Indeed, I was thinking about the sending /receiving limits