Gmail switch affect php apps like zencart?

hope someone can give me some info or direct me to a prior answer:
I recently installed the zencart one click install. The email send function in zencart uses php as the transport method and setup was transparent to me (I did not have to set anything). If I switch from dreamhost mail to gmail, will this stop working? Would I have to change to some settings (transport method, host settings, etc.) to get it to work?
This question is probably not specific to zencart, as any app using php transport would seem to be related. Thanks.