Thanks jvstratum!
Yes, I'm sure I have rebound. I access my mailbox and there they are (some in spam). It is a Google email account. Our version is Enterprise, that is, the paid one.
I have doubts about the "Enable automatic bounce handling" option, as I don't have it checked. Is it necessary to do so for me to manage it? Also, if they reach Spam, I understand that they will not be recorded in the statistics, only those that are in the inbox.
Finally, is it also necessary to have cron activated?
Thanks again.