Can't Edit Appointments After Migration
Resolve calendar editing issues caused by unrecognized organizer addresses.
The Problem
Symptom
After migrating to Office 365, users cannot edit their own calendar appointments. They receive errors or find the editing options grayed out for meetings they originally created.
Common behaviors: Edit button disabled, "You don't have permission" errors, or changes not saved when editing recurring meetings.
Why This Happens
Root Cause
X.500 Address Mismatch
In Exchange and Office 365, calendar appointments store the organizer's identity using internal addresses called X.500 entries (also known as LegacyExchangeDN). When you create a meeting, Exchange records your X.500 address in the "Organizer" field.
After Migration
Your new Office 365 account has different addresses than the source system. When Outlook checks if you're the organizer, it compares your current ProxyAddresses against the X.500 in the appointment - and they don't match.
How Outlook Verifies Ownership
Outlook and OWA check if your email address, alias, or any ProxyAddress matches the "Organizer" field in the appointment. If there's no match, you're treated as an attendee, not the organizer.
Solution
Migrate LegacyExchangeDN to ProxyAddresses
The fix is to add your old X.500/LegacyExchangeDN as a ProxyAddress on your new Office 365 account. This way, when Outlook checks the organizer field, it finds a matching address in your profile.
Use Cloudiway's Transfer X500 Task
For Office 365 to Office 365 migrations, use the built-in LegacyExchangeDN migration tool under global tasks.
Verify the Mapping Table
Ensure your source and target users are properly mapped before running the X500 transfer.
Wait for Replication
Allow time for the changes to propagate through Office 365 and for Outlook to refresh its cache.
Prevent This Issue
Troubleshooting
Inspect Appointment Fields with MFCMAPI
If you need to investigate which specific addresses are stored in an appointment's organizer field, use Microsoft's MFCMAPI tool:
- Download and run MFCMAPI
- Open your mailbox and navigate to the Calendar folder
- Open the problematic appointment
- Look for properties containing the organizer's address (X.500 format)
- Compare these values to your current ProxyAddresses
What to Look For
The X.500 address typically looks like:
/o=ExchangeLabs/ou=Exchange Administrative Group/cn=Recipients/cn=user123
Key Takeaway
Calendar editing issues after migration are almost always caused by X.500/LegacyExchangeDN addresses not being migrated. The solution is to add the old addresses to your new account's ProxyAddresses so Outlook recognizes you as the organizer.