It is always part of the outlook administration job to either move, recover , repair and migrate outlook mailbox or PST. It is worthwhile mentioning that after the migration of the outlook mailbox or PST to another Mailbox or PST everything will probably look fine. Having said that, there is one thing that seldom works correctly. You may notice that in the newly migrated mailbox, all the meetings will be missing the "send Update" option. Because of this, you will be unable to send updates to the meeting attendees. The usual error is that the meeting request is not sent. The work around is simple but it is rarely mentioned on the support sites. Here is the workaround:

In order to migrate appointment from one mailbox/PST to another mailbox/PST without losing the Option  "Send Update" in calendar meetings, you need to make sure that you move the calendar items not copy/paste or export/import.  If you do a copy/Paste or Import/Export you will be unable to send updates to the meeting attendees in the destination calendar

Lets see the procedures to move the outlook calendar items

1) Just switch the calendar view to category view and move  all the calendar items by performing the below steps

Click on View->current view -> by category
click on Edit->Select all ->Cut

2) Than go to the target calendar and paste it

Click on View->current view -> by category
click on Edit -> paste

Click on View->current view -> day/week/month

Now you can open any appointment and be able to "Send Update" to the meeting attendees