Double opt-in
The person confirms their email via a link before you add them to marketing — stronger proof they meant to join.
Say it out loud
“We email them once to check the address is really theirs before we ever market to them.”
Double opt-in (also called confirmed opt-in) means that after someone submits an address, nothing marketing-related is sent until they click a confirmation link. It is the strongest ordinary evidence of consent, and it quietly filters out typos, bots and people signing up their colleagues.
Two minutes and forty-four seconds later. That gap is the evidence: a human read an email and acted.
An address that never confirmed is either a typo or someone else's. Both are liabilities.
The confirmation timestamp is the single most useful field in a consent argument, because a machine cannot produce it and a person cannot forget it.
Yours
Nobody does this for you.
What goes wrong
Sending the confirmation email and, when it is not clicked, adding the person anyway on the grounds that they clearly meant to. That is worse than single opt-in: you now have a documented record of someone declining to confirm.
What people get told
The claim. “Double opt-in costs you half your list.”
Actually. It removes the half that was never going to engage, plus the typos and the bots. The measurable effects are lower bounces, lower complaint rate and fewer spam-trap hits — which is to say, the three things that decide whether the rest of the list arrives at all.
The dated rules behind this
A definition is not a citation. These are the pages with the primary source, the date it was published, and what to do about it.
See also
Where this sits
Stop 1, you get the address. Someone hands you an email address, and the terms of that handover decide everything after it.