[vchkpw] Vpopmail/Outlook Not retrieving some email

[Rod K]

I have a situation where some users using Outlook (Office not express) 
are not able to retrieve all their emails.  The emails are sitting in 
their new folder but for some reason Outlook won't retrieve them, then 
maybe 24 - 72 hours later, they finally appear in Outlook.

Has anybody seen this behavior before and if so were you able to find a 
solution?

vpopmail 5.4.0
Outlook 2000/XP
TIA
Rod