Many thanks for this great article!
Just a little tip, in case it would help someone with the same problem:
Following the article's direction, I added
define(`confDOMAIN_NAME', `$w.my.domain.com') to the config. However, the messages I sent were rejected by other SMTP servers because the sender address looked like
myUsername@myMachineName.my.domain.com which didn't resolve to a known IP (I guess myMachineName was taken from Rendez-vous).
I fixed it by changing the confDOMAIN_NAME definition to
define(`confDOMAIN_NAME', `my.domain.com'), and now the sender of my messages looks like