To reduce the incident of income tax fraud the IRS set a limit of 5 efiled returns using the same DIY program not per email address. The 5 efiles are registered by the program you purchased and once you hit the limit no further efiling will be allowed. I don't know for sure but I also believe they track the IPN of the computer sending the efiles ... this is to stop a fraudster from buying several programs to get more filings using the same computer or bank of computers. Over the years the feds have shut down many income tax fraud rings so these rules have been put in place to stop the crooks with unfortunate side effects on the honest folk.
Now you could have some of these people that you help to file get their own program on their own computers and you go to their home and complete their returns.
