Warm-up

To an inbox provider, a brand-new domain that suddenly sends thousands of messages looks exactly like a spammer, however good the content is. The result is filtering to spam or outright blocking, often before a single recipient sees the message. Once a domain has a poor reputation it is slow and sometimes impossible to repair. Warm-up builds a good reputation on purpose, so that by the time real volume arrives the provider already has evidence that people want these emails.

• Set up the technical basics first: SPF, DKIM and DMARC records, which prove the mail really comes from you.
• Start with a small daily volume to your most engaged contacts, the people most likely to open and reply.
• Raise the volume gradually, typically over two to eight weeks, and check bounce and complaint rates at each step.
• Slow down at once if bounces or spam complaints rise. Do not push through the schedule regardless.
• Keep sending patterns steady from day to day instead of sporadic bursts.
• Move to full volume only after the signals have stayed clean for a sustained period.

Warm-up is a planned ramp in sending volume that teaches inbox providers to trust a new domain or mailbox.

A new sending domain starts with a handful of emails a day, sent to people who are likely to open and reply, and the daily number rises step by step over several weeks. Each healthy send adds to the domain's track record with providers such as Gmail and Outlook.

It applies to every new domain and mailbox, and to an old one that has been silent for months and is about to send at volume again.

• Moving an entire existing list onto a new domain on day one.
• Warming up with purchased or unverified addresses, which bounce.
• Stopping the routine sends once warm-up ends. Reputation needs steady, wanted mail to stay healthy.