Multiple email addresses in the main email field?
Sort of related to having more than one active email field...but I just came across this while integrating with QuickBooks.
We have several clients for which we have 2 email addresses in the field (separated by a comma), and when we email their invoices to them, it goes to both emails automatically.
When updating a contact record that had 2 emails from QuickBooks, I had to remove an email address to be able to save it because it only allows one.