We're facing an issue with Microsoft Exchange 2003 where a large (around 10GB) shared mailbox accessed by a number of users is duplicating messages sent out, and recipients are getting multiple copies. In Outlook's Sent Items for the mailbox there is only 1 copy of the message.
The message is getting processed by Exchange 2003 on SBS 2003, and is then handled by Mailmarshal. By the time Mailmarshal gets the messages, they're duplicated but with unique IDs, and from the checks I've seen in the Exchange logs, they're unique IDs by the time they get there too, so am I right in thinking that the Exchange server itself, and Mailmarshal, aren't causing the problem?
Some of the messages have multiple recipients, internal and external, but some only have a single recipient. Duplicates appear to be random and can be anything from 2 to 6 copies.
Is it possible that it's the mailbox size causing the issue? Before the problem arose the mailbox size had previously been at around 12GB, but had already been reduced in size.
