B2B cold email deliverability checklist

Short answer: Send cold email from separate, authenticated domains with SPF, DKIM and DMARC. Warm up new mailboxes slowly, keep daily volume per mailbox low, stop sequences the moment someone replies, and check mailbox health every week.

Should you send from your main domain?

No. Use one or more secondary domains for cold outreach, such as a close variation of your brand name. If a cold campaign damages a domain’s reputation, your main domain keeps delivering invoices, product email and replies to customers.

Point the secondary domains’ websites to your main site, and make sure the sender name and signature clearly show who you are.

Which DNS records do you need?

Every sending domain needs three records:

• SPF: lists the servers allowed to send email for the domain.
• DKIM: adds a cryptographic signature that proves the email was not altered.
• DMARC: tells receiving servers what to do when SPF or DKIM fail, and where to send reports. Start with a monitoring policy, then tighten it once reports look clean.

Also set up a custom tracking domain if you track opens or clicks, and confirm that every mailbox passes all three checks before it sends a single cold email.

How should you warm up new mailboxes?

New mailboxes have no sending history, so receiving servers treat them with caution. Build that history gradually:

• Start with a small number of emails per day and increase slowly over several weeks.
• Send real, low-risk email first: replies, introductions and conversations that get answers.
• Watch bounce rates and spam placement as volume rises, and pause if either worsens.

What sending limits are safe?

There is no single safe number, but the principle is consistent: keep volume per mailbox low and spread it across mailboxes and domains instead of pushing one mailbox hard. Send at a steady pace during business hours rather than in bursts.

Large email providers publish requirements for bulk senders, including authentication, easy unsubscribe and low spam complaint rates. Cold outreach should stay well inside those rules, not near their limits.

How should replies and bounces be handled?

• Replies: stop the sequence for that prospect immediately, including automated follow-ups. A follow-up after someone has replied damages trust and invites spam reports.
• Bounces: remove hard bounces at once and never retry them. A rising bounce rate usually means the lead data needs cleaning.
• Opt-outs: honor every unsubscribe request across all mailboxes and future campaigns.

What should you monitor every week?

• Bounce rate per mailbox and per domain.
• Reply rate per mailbox, segment and message.
• Spam complaints and blocklist status for each sending domain.
• SPF, DKIM and DMARC results, including DMARC reports.
• Inbox placement on a small seed list across major providers.

If one mailbox’s numbers drop while others stay steady, pause it and investigate before it affects the rest.