Glossary · Cold email
What is email deliverability?
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Definition
Email deliverability: The share of sent emails that actually reach the recipient's inbox (vs. spam folder, blocked, or bounced).
Deliverability is downstream of: domain reputation (warm-up history, sending consistency), authentication (SPF, DKIM, DMARC all aligned), content (spam-triggering phrases, link density, image-to-text ratio), and behavior (open/reply/spam-report ratios from past sends). Inbox-placement testing tools check where messages land across Gmail, Outlook and Yahoo.
What affects email deliverability?
Four things: authentication (SPF, DKIM and DMARC set up and aligned), sender reputation (your domain's and IP's history of bounces, complaints and engagement), sending behaviour (steady volume rather than sudden spikes), and content (clear, relevant messages without spammy formatting). Reputation is the slowest to build and the quickest to lose.
What does Gmail require from senders?
Gmail asks every sender to authenticate with SPF or DKIM, have valid forward and reverse DNS, use TLS and keep spam rates in Postmaster Tools below 0.3%, ideally under 0.1%. Bulk senders above 5,000 messages a day must also set up DMARC and support one-click unsubscribe on marketing messages.
How do you measure deliverability?
Watch bounce rate and spam-complaint rate per mailbox, check your domain in Google Postmaster Tools, and run inbox-placement tests that send to seed accounts at Gmail, Outlook and others to see where messages land. Reply rate is a useful lagging signal: a sudden drop often means messages started landing in spam.
How do cold email senders protect deliverability?
Send from a separate domain or subdomain, warm up new mailboxes gradually, verify every address before sending, keep daily volume per mailbox modest, include an easy opt-out and honour it, and stop sequences as soon as someone replies. Spread volume across several mailboxes rather than pushing one hard.
Related terms and pages
- Warm-up (email)
- Gradually increasing the daily send volume from a new email mailbox or domain to build sender reputation with inbox providers such as Gmail and Outlook.
- SPF / DKIM / DMARC
- Three DNS-level email authentication standards that tell receiving inbox providers your messages are legitimately from your domain. All three should be configured for any cold-email sender.
- Cold email
- Unsolicited outbound email to prospects who haven't opted in, sent for B2B sales, recruiting or partnership purposes. Legal in many jurisdictions under specific conditions; ineffective without deliverability infrastructure.
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