Originally Posted by thedaver
There was a time when yahoo had traces of qmail in their server messages... that might be a long time ago by some standards.
I think it's safe to say they've built into heavily customized versions of available FOSS. I would bet against sendmail.
I also think same but just want to be sure.
Just now I found that gmail use "Gmail runs on Google GFE/2.0 on Linux. As of June 2012,"
anyway waiting for more reply.