Most administrators discovered long ago that ExMerge is a mail admin's best friend. You can use ExMerge for everything from backups to disaster recovery to mailbox moves. However, even this old standby has its limits.
The personal folders file (PST) size limit is one of ExMerge's problems. A PST's total file size can't exceed 2 GB. Since ExMerge extracts mailboxes to PST files, it's tricky to use ExMerge on mailboxes that approach or exceed this limit.
The best way to work around the file size limitation is to extract the mailbox into two or more PST files, based on date. Open the ExMerge utility, enter the name of the Exchange server you're copying from, and click Options. In the Data Selection Criteria dialog box, select the Dates tab. From here, you can extract the mailbox contents to a PST file based on message dates.
You can use this method to extract fractions of the mailbox information so you can keep each PST under 2 GB. Keep in mind that ExMerge loses single instance storage, which means the PST files' total size will be larger than the mailbox itself.
Extracting a mailbox into several PSTs requires some juggling, but it's the only way to get a large mailbox into PST files. It's just one more reason to implement mailbox size limits in your organization.