Many thanks for the info!
I will try to explain how my app works with the e-mails: I had one which was suporte.meustickers@rpaladino.heliohost.org that was used to receive e-mails from users, so this mailbox was configured to receive e-mails. Also, I had one more which was services@rpaladino.heliohost.org that was used to my app send e-mails to users, like account activation or alerts. This one was setup to not receive e-mails.
I'm sorry, but my knowledge on how to configure network services is very limited...
May the domain you referred be the one I already have on heliohost (rpaladino.heliohost.org)? Would be possible to have 2 accounts: one for users to send e-mail to me so I could reply them and one that only my app could use? If not, I was think on setup a google e-mail to it, but it me and my app would use.