Hi,

We've built an outlook plugin that requires setting user properties to associate client & custom information with a particular mailItem. Currently we are creating an email web client and want to transfer and access those user properties on the web client.  Are these properties bundled into the message header or stored on exchange and retrieved through a saved key. How can I access these properties, on another mail server, do I have to transfer these to MAPI fields? 

Thanks,
Mil

You can access any user properties you create in your Outlook plugin in EWS using the Extended property interfaces see https://msdn.microsoft.com/en-us/library/office/dn467898%28v=exchg.150%29.aspx . The only thing you can't do with EWS is read or write the userproperty definition blob (which just means you can't enumerate what properties a user has created). That should really be issue however all you need to do is use a MAPI editor like MFCMapi or Outlook Spy to look at an existing item where the properties have set you should then be able to use them like

ExtendedPropertyDefinition UserProperty = new ExtendedPropertyDefinition(DefaultExtendedPropertySet.PublicStrings, "MyCustomProperty", MapiPropertyType.String);

Cheers
Glen

You can access any user properties you create in your Outlook plugin in EWS using the Extended property interfaces see https://msdn.microsoft.com/en-us/library/office/dn467898%28v=exchg.150%29.aspx . The only thing you can't do with EWS is read or write the userproperty definition blob (which just means you can't enumerate what properties a user has created). That should really be issue however all you need to do is use a MAPI editor like MFCMapi or Outlook Spy to look at an existing item where the properties have set you should then be able to use them like

ExtendedPropertyDefinition UserProperty = new ExtendedPropertyDefinition(DefaultExtendedPropertySet.PublicStrings, "MyCustomProperty", MapiPropertyType.String);

Cheers
Glen

• Proposed as answer by Jason Johnston [MSFT]Microsoft employee, Moderator 16 hours 12 minutes ago

Hi Glen,

So If I'm accessing the messages through Imap4 and those properties would only be available on an exchange server environment. I would not be able to get them from msg object, or anything correct? 

Not using IMAP no I would suggest that you use X-Headers instead which will work okay across IMAP, EWS and MAPI.

Cheers
Glen