Show a block only to some people
One rule on any block or section: who sees it, and who gets the email without it.
EmailAny block in the designer — a paragraph, a button, a picture, a whole section — can carry a rule: show this only when…. Tick “Show this only to some people” in the panel on the right, pick what to test, and everyone the rule does not match receives the same email with that block quietly missing. One send, several versions of itself.
What you can test is anything the reader carries: the merge tags this workspace actually sends (the box offers them, so you pick rather than guess a spelling), plus first_name, name and brand. The operators are deliberately plain — has any value, is empty, is exactly, is not, contains, is a number greater than, is a number less than.
“Has any value” is the workhorse. A tag nobody has is simply empty, so “show when order_number has any value” is the honest way to say “only people with an order”. A number comparison against something that is not a number hides the block rather than guessing at it.
It is one condition per block, on purpose. An email whose layout depends on a boolean expression is one nobody can proof-read before it goes to forty thousand people; two blocks with opposite rules say the same thing and can be read at a glance. The stage marks every block that carries a rule, so you can see at a glance which parts of the email are conditional.
The designer, the preview, the HTML export and a test send always show every block — you could not edit or proof-read what a rule had hidden. The real send is the only place the rules apply.
Links keep working. When a block is hidden from somebody, its links leave their email with it, and a click from that person still lands where the link they saw pointed.