Microsoft has no hidden limits. PST files are subject to a 2GB or 32GB
limit depending on their type. Mailboxes have performance issues when they
get too big, or if any one folder has more than, say, 2,000 messages, but
there is no hardcoded limit. A single mailbox can be as large as the
mailbox store's maximum (as with Standard Edition) or the volume size,
whichever is smaller.
MVP - Exchange
"Protecting the world from PSTs and brick backups!"