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. The problem was that the Exchange 2010 migration had never been completed. When trying to open the Address Lists in the Exchange Management Console we received the following error.
The specified address list could not be edited. Address lists created by using legacy versions of Microsoft Exchange must be upgraded by using the "ForceUpgrade" parameter of the "Set-AddressList" cmdlet.
It quickly became clear that this must be our issue so, we upgraded our Address Lists to Exchange 2010. For instructions on how to do that, please check out this article:
Upgrade Address Lists from 2003 to 2010
Once upgraded we then instructed the Offline Address Book to regenerate. This is key, as most Outlook clients are typically operating in cached mode, which works off the Offline Address Book and not directly off the Global Address List.
To do this complete the following steps.
- Open the Exchange Management Console
- Expand Microsoft Exchange On-Premises
- Expand Organization Configuration
- Select Mailbox
- In the main pane, select the Offline Address Book tab.
- Right-click on your address book and select Update from the context menu.
- Select Yes to confirm.
As identified on the confirmation dialog, this may take several minutes to regenerate. In fact, it could take a lot longer than that. Give it a good fifteen minutes. Keep an eye on the Event Viewer for any failure notifications.
Once regenerated we then needed to instruct Outlook to download the entire Offline Address Book. By default, Outlook will only download incremental changes and this will not work. To download the full Offline Address Book in Outlook 2013, complete the following steps:
- Open Outlook 2013.
- Select the Send / Receive tab.
- Select the Send / Receive Groups button.
- Select Download Address Book… from the context menu.
- Uncheck the box Download changes since the last Send/Receive.
- Make sure Global Address List is selected in the Choose Address Book dropdown.
- Click Ok.
- Wait for the Address Book to download. This takes a few minutes.
At this point, you should be good. Before you retest, make sure your users on both sides, sending and receiving, download the full address book.
I hope this helps. Let me know your own findings by leaving a comment. I would love to hear what you did!