Emails not sending if domains don't match

For years our company intranet only had users with emails ending in @imagesourceusa.com

Recently our parent company is now adding people with emails ending in @visualedgeit.com

When someone fills out a gravity form emails we need it to come from the person sending it (so it goes into our tracking system correctly). The problem is that emails are NOT BEING SENT from our @visualedgeit.com users.

How can I get both to send?