Thanks for your continued help and for sharing your config.
I got the yahoo/gmail solved but my emails go to their spam... I will try to add DKIM and DMARC next to see if it helps. Hotmail is tougher, they refuse my email based on some IP filtering they have for my hosting provider. So, I am trying to add some abuse@siteX.com and postmaster@siteX.com in order to join their SNDS and JMRP as they suggested. Not sure if it will help.
I am trying different ways to create those abuse and postmaster emails for all my web sites with the least amount of email accounts.
I think aliases worked for site1 when I added:
postmaster: postmaster@site1.com
abuse: postmaster@site1.com
But I am having trouble forwarding the other sites to site1 in order to have only one email account for all these. I tried different things and the latest I tried is by adding this in file virtual:
abuse@site2.com abuse
postmaster@site2.com postmaster
abuse@site3.com abuse
postmaster@site3.com postmaster
It seems like it is trying to send to postmaster@mail.site1.com which dovecot does not find, and it discards those emails. Not sure what is the easiest way of doing this.