Sort every mailbox you own from one account. Each additional mailbox is $4.49 a month ($39.50 a year, $69.50 for 2 years) at the founding price, $6.49 a month ($49.50 a year, $84.50 for 2 years) after — on the same cadence as your own plan, prorated when you add it and credited when you remove it. All your mailboxes share one set of categories and rules, and one daily digest covers them all.
One set of categories and rules
Categories, rules and corrections belong to your account rather than to a mailbox. A correction you make on one inbox applies to the same sender wherever they write to you.
Adding one
Inboxes → Add inbox, then the same consent flow you went through the first time. Billing updates pro-rata for the rest of the current period.
Sortmail is a single-person tool. Additional inboxes are for your own mailboxes, not for sharing an account with colleagues — shared and team inboxes are not supported.