Email Deliverability Best Practices: Getting Into the Inbox, Not the Spam Folder
Deliverability is the unglamorous half of email marketing that determines whether any of the other work — design, copy, offers — ever gets seen. Inbox providers like Gmail and Outlook are constantly deciding whether your emails belong in the inbox or the spam folder, based on a mix of technical setup and how recipients actually treat your messages. This guide covers the fundamentals in plain English.
What deliverability actually means
Deliverability is simply the percentage of your emails that reach the inbox rather than getting filtered to spam or blocked outright. It's decided by inbox providers looking at two broad things: whether your email is technically verified as genuinely coming from you, and whether people who receive your emails treat them like wanted mail or unwanted mail.
SPF, DKIM and DMARC, without the jargon
These three are technical records that prove an email genuinely came from your business and wasn't faked by someone else pretending to be you. You don't need to understand the underlying mechanics to benefit from them — you just need them set up correctly, usually once, by whoever manages your sending platform.
The plain-English version
You don't have to configure these yourself
Getting SPF, DKIM and DMARC right involves editing DNS records, which is a common place small businesses get stuck or make mistakes. Havari sets this up as part of onboarding, so a new sender's domain is properly authenticated from the first campaign rather than left as a manual task.
Sender reputation
Beyond the technical checks, inbox providers track a reputation score for every sending domain and IP, built from how recipients behave — opens, clicks, replies, deletions without opening, spam complaints, and bounces. A strong reputation, built up over time, is what earns consistent inbox placement even during busier sending periods.
What damages sender reputation
List hygiene
A clean list is one of the simplest levers available for better deliverability, because every metric a sender reputation is built from — opens, bounces, complaints — is calculated against the list you're sending to. A smaller, well-maintained list will consistently outperform a larger, neglected one.
Keeping a list clean
Remove hard bounces immediately
A hard bounce means the address doesn't exist. Continuing to send to it signals a poorly maintained list to inbox providers.
Move long-term inactive contacts out of regular sends
Contacts who haven't opened anything in months should move into a re-engagement flow rather than continue receiving every regular campaign.
Honor unsubscribes and complaints instantly
Anyone who unsubscribes or marks an email as spam should never receive another campaign — this is both good practice and, in most cases, a legal requirement.
Re-verify old, unused lists before reactivating them
A list that hasn't been emailed in a year or more should be treated cautiously and warmed up gradually rather than emailed in full immediately.
Avoiding spam trigger language
Spam filters also look at the content of the email itself. While modern filters weigh engagement more heavily than exact wording, certain patterns still raise flags, especially combined with poor sender reputation.
Content habits to avoid
Before and after a spam-flagged subject line
Before: "!!! ACT NOW - FREE MONEY WAITING - CLICK HERE !!!" After: "Your £10 credit is ready to use"
“Deliverability isn't a one-time setup — it's an ongoing reputation built by how recipients treat your emails.”
Do I need to set up SPF, DKIM and DMARC myself?
If you're using a platform that manages sending infrastructure for you, such as Havari, this is typically configured as part of onboarding rather than left to you as a manual DNS task.
Why did my emails suddenly start going to spam?
Common causes are a sudden spike in sending volume, a rise in spam complaints or bounces, or emailing a list segment that's gone stale. Reviewing recent list hygiene and engagement is usually the first place to look.
How long does it take to build sender reputation?
It builds gradually through consistent, engaged sending over weeks and months rather than instantly. New senders should expect a gradual warm-up period before sending at full volume.
Good deliverability comes from a combination of correct technical setup and genuinely wanted email — there's no shortcut around either one. Get the authentication right once, keep the list clean on an ongoing basis, and write subject lines and content that read like a message a real person wants to open, and inbox placement tends to take care of itself.