Definition
Warm-up is the practice of starting a new sending domain, mailbox or IP address at low volume and increasing it step by step over several weeks. Mailbox providers have no history for a new sender. A sudden burst of mail from an unknown source looks like spam, while a steady, growing stream with good engagement builds a positive record.
There are two common approaches:
- Manual warm-up. Start with a small number of emails a day to people likely to open and reply, then increase gradually.
- Automated warm-up tools. Services that exchange emails between a network of participating inboxes, open them, reply and move them out of spam to generate positive signals.
Cold email teams usually warm up every new domain and mailbox before adding them to a sequence, and many keep some warm-up running alongside campaigns.
Why it matters
Skipping warm-up is one of the fastest ways to burn a new domain. The first large send from a cold domain often lands in spam, and the reputation damage lingers.
Warm-up has limits. Automated tools create engagement within their own network, which is not the same as real recipients replying to you. Providers can learn to discount those patterns. And no amount of warm-up protects a domain from a bad list. A freshly warmed domain that sends to a list full of dead addresses will lose its reputation as quickly as it gained it.
How SimpleCold handles it
SimpleCold does not run warm-up. It makes sure the first real sends after warm-up go to addresses that exist. Verify your list before day one of the campaign, remove Undeliverable results, and hold back Risky groups such as catch-all addresses until the domain has a track record. Sending the cleanest contacts first gives a new domain the best start.