Hi Jaime! This does not look to be implemented functionality at this time as I'm not seeing a conflict indicator on invites from SmarterMail users or external senders. I can definitely see that being helpful though so I'll go ahead and write up a feature request on this and send it over to our Product Management team for review. Thanks for the great suggestion!

Thanks Kyle!  I hope it gets implemented.

You're very welcome Jaime. I got that escalated for review along with a link to this post so we can use this to gauge user support.