Please can you advise how many contacts ( i.e. the total limit number ) that Outlook can hold?
Early versions of the Exchange client supported about 16,000 items per folder. Outlook, with large table support enabled, supports about 65,000 items per folder. (Large table support is the default for new pst's created since Outlook98.) Outlook 2003 with a Unicode format *.pst or *.ost can have an unlimited number of items.
These limits apply to all folder types and subfolders count as 'items', so you could have 60000 folders and 5,000 messages, with each of the 60,000 folders containing 65,000 messages, at least until you hit the ANSI pst size limit of 2GB.
Exchange mailboxes should not be affected by these limits, except when using it offline.
As your folders (and the mailbox) grows, it tends to slow Outlook down, so while you can have 65,000 contacts, you may not want quite that many.
Published December 23, 2003. Last updated on January 30, 2016.