THIS IS NOT ACCEPTABLE 
This is NOT a FEATURE you can sell, this is a MUST.
We didn't pay software to create problems instead to solve them.

People especially non-IT people can forget to add PO number to email subject.
Now since email clients combine same subject emails under same thread.
All our PO mails intended for different vendors are combined under the same email thread.
And our non IT stuff , replying those emails ,occasionally sending those emails to non-intended vendors.
This is a total MESS.

We won't be paying to QBooks to solve a problem , it creates.
We will consider quickest way to get out of it.