How to compare the MAPI property differences between Outlook emails
I was recently working on extracting mail from Outlook to an .msg file and later importing the .msg file back into Outlook. I was concerned that some of the non-obvious properties (there are a lot of non-visible MAPI properties stored on an email) would not be persisted or may change value in the process of the export/import. I thought this was going to be a daunting and time consuming process comparing the value of around 100 MAPI properties and playing spot the difference. Luckily the first thing I tried was the awesome OutlookSpy tool which I’ve found simply brilliant for assisting with Outlook development over the years. What I didn’t realise was that OutlookSpy has a build-in compare feature that will compare the MAPI properties of 2 mail items and highlight:
- Properties missing/extra on the 2 objects being compared
- Properties with different values on the on the 2 objects being compared
- Properties with the same values on the on the 2 objects being compared
Steps compare the properties on 2 email messages using OutlookSpy
Select one of the emails to compare and select OutlookSpy | IMessage
The IMessage window will appear showing all the MAPI properties on the item. From here select the Compare tab.
In order to compare this email against another email, the compare tab gives you a green area where you can drag and drop the PR_ENTRYID property from a different email message. So to do this leave the IMEssage window open on the compare tab.
Go and select the email you want to compare to in Outlook and select the OutlookSpy | IMessage button for this new email. You will be presented with the IMessage window and shown the MAPI properties for the new email. Locate the PR_ENTRYID MAPI property in the table (hint: click the column header to sort the table). Now drag and drop the PR_ENTRYID row from the table into the green drag/drop zone on the original IMessage window that you left open.
Now the magic happens! The compare tab does a comparison of the 2 items and allows you to switch between properties with the same values, properties with different values, and missing or extra properties.