Q:

How many bounces before removing a dead address to avoid recycled spam trap?

We are developing our own mailing tool and scan log and mail error to remove dead mails from our database. 
When an error 5xx is returned by mails servers, we remove the mail for a determined time (eg 80 days). 
We do this because we want to try again later, if the user recreate his mail account, or if the domain shows up again atfer have been offline (because his ownwer forgot to renew it), this user will expect to still receive mails. 
But I’ve discovered today the concept of dead or dormant address, and I want to avoid recycled spam traps. 
Is it better to remove the bounced mails definitely from our database? What if the user’s mailbox comes back later?

A:

You should never subscribe someone to your list without their permission, which is exactly what you are doing. If that email address does get reactivated, you have no way to know if it is the same person or not. So your email would then be unsolicited, and safely considered spam.
If you get a 5xx bounce, you should permanently unsubscribe the address.

