If you are a LinkSeam WhiteLabel user you can set branded onboarding email for your WhiteLabel clients' Team onboarding. 

When setting up your WhiteLabel option you need to use an email under your WhiteLabel domain in White Label Email field. 

When this is set-up, after you add clients under your WhiteLabel account, when your WhiteLabel clients invite their Team Members, those Team account invites will go from this WhiteLabel email ID you entered.

However, these onboarding emails may sometimes go to Spam. So kindly alert your WhiteLabel clients to inform their team members to check Spam or Junk Email folder in case they don't find the onboarding email in their inbox.