Content
The secret to landing in the inbox
Delivery gets the server to accept your email. Deliverability gets it into the inbox — and that's the one that dictates performance.
Email marketing is a two-step equation: before a subscriber can engage with your message, the message has to reach them. Many marketers conflate delivery rate (whether the receiving server accepted the email) with deliverability (whether it landed in the inbox versus the spam folder) — and it's the latter that truly dictates campaign performance.
As Mailchimp's research emphasizes, deliverability is a continuous feedback loop. ISPs like Google and Yahoo act as gatekeepers, evaluating your sending habits to protect their users' inboxes. To survive those automated filters, you have to actively optimize the pillars of sender health.
Prove your identity with authentication
Before an ISP checks your content, it checks your identity. If your setup looks anonymous or unverified, filters flag the message as a phishing risk. Per HubSpot's deliverability frameworks, authenticity requires three DNS records:
- SPF (Sender Policy Framework): specifies which mail servers are authorized to send on behalf of your domain.
- DKIM (DomainKeys Identified Mail): adds a digital signature proving the message wasn't intercepted or altered in transit.
- DMARC: tells receiving servers how to handle mail that fails SPF or DKIM — shielding your brand's reputation.
Avoid sudden volume spikes
A sudden spike in volume is one of the quickest ways to trip a spam filter. If a brand-new domain or dedicated IP fires out 50,000 emails in a day, algorithms assume the account is compromised. The fix is a disciplined warm-up: start with low volumes to your most engaged subscribers and ramp frequency and volume over a 30–60 day window, so inbox providers can recognize your patterns and build a baseline of trust.
Step away from unengaged subscribers
Modern spam filters are behavioral — they watch how real humans interact with your content. A large share of unengaged contacts signals to ISPs that your content may not be valuable. Use automated settings to pause or stop messaging anyone who hasn't opened in 60–90 days, so dead weight doesn't drag down your placement for everyone else.
Build positive engagement loops
Focus on generating positive signals: opens, clicks, dragging a message out of the promotions tab, replies — all tell algorithms your content is wanted. High bounce rates and spam complaints are immediate penalties. Treat your strategy as a deliverability asset by heavily segmenting sends so messages land with the audiences most likely to read and interact.
Deliverability isn't a one-time chore; it's an ongoing strategy. Lock down authentication, pace your volume, and pause sends to unengaged profiles, and you stop fighting the filters and start building a permanent pathway to the inbox.