Your first day is when the inbox gets quiet. Here is what happens, roughly in order.
The first sync
Sortmail looks at the last 30 days of your inbox and sorts it, showing each message with the reason it went where it did. You can watch the rows fill in. This first sort is free: nothing is written to your mailbox until you choose a plan.
Older mail
The first sort covers the last 30 days of your inbox, up to 1,000 messages, newest first. Anything older is not sorted automatically, on any plan: Sortmail leaves it exactly where it is and applies no label to it. If you want it out of your inbox, archive it yourself — in Gmail, search in:inbox older_than:30d, select all and archive; in Outlook, sort the inbox by date and move the older messages to Archive. Everything that arrives from then on is sorted as it lands.
The first hour
Expect to correct a handful of messages. Newsletters from people you actually know, and receipts that read like personal mail, are the usual ones. Every correction becomes a rule for that sender straight away, so their new mail goes where you put it.
The first day
Because each correction becomes a rule, the number you need to make should fall. The Accuracy card on the first screen — the share of each category you did not move — shows whether it is.
The first digest
The morning after you connect, you get your first digest at 8am: what arrived, what stayed in your inbox, and what was filed and why — how each filed message was decided, and which ones Sortmail was less sure about. If you would rather have it at another hour, or not at all, change it on the Digest page — the hour is in your own time zone. With Skip quiet days on, a day where nothing stayed in your inbox and every filing was a confident call sends nothing.