Transactional Email.

Transactional emails are the quiet workers of a website or web app. A customer orders in a shop and receives a confirmation. A patient books an appointment and gets a confirmation with the address. A team member signs in and receives a six-digit code. A prospect downloads an e-book and gets the download link. What they all have in common: the email is triggered by an action, it goes to exactly one person, and that person expects it, often within seconds.

A transactional email should be distinguished from email marketing. A newsletter goes to many recipients at once and aims to inform or sell. A transactional email meets an expectation arising from an existing relationship. The line blurs when companies pack order confirmations with advertising. Legally this matters: Switzerland's Unfair Competition Act (SR 241, Art. 3 para. 1 let. o) governs mass advertising by email. A plain confirmation is not advertising; a confirmation that mainly contains offers may be assessed differently. This is general guidance, not legal advice.

Technically, transactional emails are usually not sent through the normal mail client but through specialised sending services with a programming interface (API), for example Resend, Postmark or Amazon SES. The website or app calls the service as soon as the event occurs. Correct authentication with SPF, DKIM and DMARC is essential, as is a sender address people can reply to and logging, so that you can see whether and when an email was sent and delivered if someone asks.

Because these emails are business-critical, they should be sent separately from marketing emails, ideally via a dedicated subdomain or sending stream. That way the deliverability of a login code does not suffer because a newsletter caused many unsubscribes or complaints. As for content: short, clear, the essentials at the top, readable on a phone and with a way to reach the company. Personal data in such emails should be kept to a minimum under the Swiss Data Protection Act (FADP, SR 235.1).