Deliverability

Delivery and deliverability are different things. An email is delivered when the receiving server accepts it; it is deliverable, in the useful sense, when it then lands in the inbox where a person will see it. Mailbox providers such as Gmail and Outlook decide that placement from many signals: whether the message is authenticated with SPF, DKIM and DMARC, the reputation of the sending domain and its IP addresses, how many recipients mark similar mail as spam, how many addresses bounce, and how people engage with it.

For outbound, deliverability is mostly decided before anything is written. Send from a separate domain set up for the purpose, authenticate it, warm up new mailboxes gradually, keep daily volumes per mailbox low, verify addresses before sending, and stop at once when bounces or complaints rise. Large providers publish requirements for senders.

• In Outlevo: A campaign pauses itself above 3% hard bounces or 5% unsubscribes over its last 200 sends, or at a spam complaint.

Sources: Gmail email sender guidelines (support.google.com, checked oct 22, 2026); Yahoo sender best practices (senders.yahooinc.com, checked oct 22, 2026).