Double Opt-in.

With a single opt-in, typing an address into the form is enough. The problem: anyone can enter any address there, including someone else's. Double opt-in adds a second step. The system sends a confirmation email, and only a click on the link inside it proves that the person has access to the mailbox and really wants the newsletter. The date, time and source of the confirmation are stored.

Swiss law does not expressly require double opt-in. The UWG does, however, require consent for bulk advertising by email, and in a dispute the sender has to prove it. Double opt-in is the simplest way to do that. Anyone who also has recipients in Germany or Austria can hardly avoid it anyway, because case law there practically presupposes it.

An example of a good confirmation email: the subject line 'Please confirm your subscription', one sentence on what the emails are about and how often they arrive, a large 'Confirm subscription' button and a note that nothing happens if you do not click. No advertising, no images that slow down loading. The plainer it is, the higher the confirmation rate.

A side effect is a better-quality list. Typos, disposable addresses and spam sign-ups never reach the mailing list in the first place. That improves the deliverability of every later email, because mailbox providers penalise senders with many invalid addresses. More on the channel under email marketing. Double opt-in belongs on every newsletter sign-up, including on a new website. How to measure sign-ups as a goal without bypassing consent is a topic for conversion tracking.