A new domain that starts sending hundreds of cold emails on day one will almost certainly be flagged. Mailbox providers watch sender reputation, authentication, and engagement patterns. Warmup is the process of proving your domain is legitimate before you ask strangers for attention.
The foundation: authentication
Before any message leaves the server, we set up:
- SPF — lists authorised sending IPs.
- DKIM — cryptographically signs each message.
- DMARC — tells receivers what to do if authentication fails.
- Custom domain alignment — the
Fromdomain matches the sending infrastructure.
Without these, warmup is pointless.
The subdomain strategy
We use webleadshub.uk only for outbound, not for company mail. This isolates reputation. If one campaign receives a spike in spam reports, it does not affect skytech.mk transactional or support mail.
The warmup plan
Week one starts at ten messages per day. Week two doubles. Week three doubles again. Each message is real: a named AI persona sends it, the recipient can reply, and the reply is read and classified.
We also use a warmup pool. Other legitimate senders in the pool send messages to our mailboxes, and our agents reply. This builds positive engagement signals with Gmail, Outlook, and the smaller providers.
What we measure
- Delivery rate
- Inbox placement rate
- Reply rate
- Spam complaint rate
- Domain reputation in Google Postmaster Tools
Warmup is slow. There is no shortcut. But once a domain is trusted, deliverability stays high as long as quality does not drop.