The automated information provided by QuickBooks does NOT address the email address issue being experienced by numerous QuickBooks clients. 

I actually spoke with a person in QuickBooks IT who took the time to review the issue concerning email addresses not populating correctly when using Projects and he fully could see and verified that an issue does exist.  When he attempted to escalate the issue, he was told that the platform is working as designed and no changes will be made at this time to address this issue.    

Shortly after that call, all of my QuickBooks investigations were closed and I was told that there are no other avenues to addressing the issue.

Work around I found includes........

1-Updating email addresses within and upon the most current Client invoice you have in that Project.

2-When building a new invoice for this Project, you can then use the most recent invoice for that Project (which has the correct email address) and you then "Duplicate" the invoice so that the information transfers correctly over to the new invoice.

3-Alter the services of the new invoice so it is correct and then send that invoice.

4-Also update the email address in the "Clients" main profile so that you have this correctly stated.