Hey @dnizhebetskiy53! We'll never send a subscriber the same sequence email more than once. So if they've already gone through the welcome sequence before, received all the emails, and then get added to that same sequence again, they won't receive the same emails again; they'll just skip over it.
The exception is if you add additional emails to the end of the sequence before they get re-added, in which case they'll receive those newly added emails only (assuming they're not filtered out of them by other means). We have more info on how sequence sending works in this context here111 :)