I guess spf would help deal with the whole apache at locahost or apache at myserver.myserver.com issues. Sending from an application is not hard for the return, from and to and all that. But the received from headers are gotten by the receiving client going to sendmail for a helo/ehlo. However apache is the user that sent it and it is the user the ehlo will look for. Since there is no way to magically make apache deal with all the virtual hosts, it is a constant problem with many webmasters. No one wants to see that in the headers anywhere. However, maybe the spf can allow apache at hostname in the dns of each domain name...thus no redflags. I can see no other good alternative for that yet.