Transactional email is a message sent one-to-one in response to something a user did or something that happened to their account: order confirmations, password resets, login codes, invoices and security alerts.
Why it matters
Recipients expect these immediately, so delays or spam placement directly hurt the product; a missing reset email can mean a lost customer. Because they are triggered and wanted, they generally enjoy higher engagement than marketing mail. Many teams send them through a separate subdomain or provider stream from bulk email, so a marketing complaint spike cannot hurt critical mail. They still need SPF, DKIM and DMARC alignment. Adding promotions to them may change how laws treat them.
Example
A password reset flow:
From: Example <no-reply@mail.example.com>
Subject: Reset your password
Body: Use this link within 30 minutes: https://example.com/reset?t=...Sent from mail.example.com, which has its own DKIM key and reputation separate from news.example.com used for newsletters.
Common mistakes
- Mixing marketing and critical mail on one IP and domain.
- Using
no-replyaddresses that cannot receive replies about problems. - Not monitoring delays, which for greylisted first mail can break one-time codes (see greylisting).
Related
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This page is general information written by our editorial team and updated when documentation changes. Servers and providers differ, so test changes safely first. See our editorial policy and disclaimer.