I ran into a strange issue recently where users could not share Outlook Calendars with one another. This problem spawned multiple symptoms and multiple errors. The environment was Exchange 2010. It affected every version of Outlook.
When users attempted to create a calendar sharing request they would receive the following error.
Error while preparing to send sharing message.
Sometimes the users could bypass this by sending through Outlook Web App. Although this was seldom a guaranteed workaround. Outlook users on the receiving side would get an error like this.
The folder you selected is not available.
If they tried to open that same message in OWA they would get this message.
This message has become corrupted. If the message is from someone else, ask the sender to send it again. If the message is in your Drafts folder, create a new message, copy text from the corrupted draft if you can, and click Save.
The fix actually turned out to be quite easy. [Read more…] about Common Calendar Sharing Errors in Outlook