Email deliverability: how to reach the inbox

Delivered isn’t the same as inboxed

When a platform reports an email as “delivered”, it only means the receiving server accepted it. Whether it then lands in the inbox, the Promotions tab or the spam folder is a separate decision made by the mailbox provider: Gmail, Yahoo, Outlook, Zoho, Rediffmail and the rest.

Those providers look at who you are (authentication), how you have behaved in the past (reputation) and how recipients react to your mail (engagement). Get all three right and the inbox follows. Neglect one and even a beautifully designed newsletter can quietly disappear.

Step 1: Authenticate your domain

Authentication lets receiving servers check that an email claiming to come from your domain really did. Three DNS records do the work. You add them once, at your domain registrar or DNS host.

DMARC only passes when SPF or DKIM passes and also matches the domain in your From address. This is called alignment, and it is why sending as yourname@gmail.com through a marketing platform no longer works. You need to send from your own domain.

MailNesto checks your SPF, DKIM and DMARC records as you add them and tells you exactly which value is missing or wrong. You can also set up a branded tracking domain, so the links in your emails use your own domain too.

The Gmail and Yahoo bulk-sender rules

Since February 2024, Gmail and Yahoo have asked more of anyone sending large volumes to their users. Google defines a bulk sender as one that has sent close to 5,000 or more messages in a day to personal Gmail addresses, and once you reach that level you are treated as one from then on. Microsoft announced similar requirements for Outlook.com in 2025.

Even if you are smaller, meeting these rules is the simplest way to stay out of spam:

• Authenticate with SPF and DKIM, and publish a DMARC record. A policy of p=none is the minimum.
• Align your From domain with SPF or DKIM so that DMARC passes.
• Support one-click unsubscribe in marketing email using the List-Unsubscribe and List-Unsubscribe-Post headers defined in RFC 8058, and keep a visible unsubscribe link in the body.
• Honour unsubscribe requests within two days.
• Keep your spam complaint rate, as shown in Google Postmaster Tools, below 0.3%. Below 0.1% is a healthier target.
• Send over TLS, from servers with valid forward and reverse DNS.

Google has moved over time from warnings towards rejecting mail that doesn’t comply. Treat these requirements as the floor, not the goal.

Step 2: Keep your list clean

Every bounce, spam trap and ignored email chips away at your reputation. List hygiene simply means mailing people who asked to hear from you and are still reading.

• Never buy, rent or scrape lists. They are full of spam traps and people who will mark you as spam.
• Use double opt-in on public sign-up forms to keep out typos and fake addresses.
• Remove hard bounces immediately, and suppress addresses that soft-bounce again and again.
• Suppress anyone who complains or unsubscribes, and keep them suppressed when you re-import a list.
• Run a re-engagement campaign for people who haven’t opened or clicked in 90 to 180 days, then stop mailing those who still don’t respond.
• Take care with role addresses such as info@ or sales@. They are often shared, and the people reading them are quick to complain.

Step 3: Warm up new domains and IPs

Mailbox providers are suspicious of a domain or IP address that suddenly sends thousands of emails with no history. Warming up means building volume gradually, so they see good engagement before you scale.

1. Start with your best contacts Send first to people who opened or clicked recently. Their positive signals set your early reputation.
2. Grow volume steadily Increase daily volume in steps (roughly doubling every few days is a common pattern) while watching bounces and complaints.
3. Pause if the numbers slip If bounces or complaints rise, hold volume where it is, clean the list, and continue only once things recover.
4. Keep a steady rhythm Once you are warm, send on a regular schedule. Long silences followed by a huge blast look suspicious.

New MailNesto accounts follow a built-in sending ramp, so volume grows as your reputation does. If you bring your own SMTP, Amazon SES or SendGrid account, the same warm-up principles apply to that sender.

Step 4: Earn engagement

Opens, clicks, replies and “not spam” rescues tell providers that people want your mail. Deleting without reading and marking as spam say the opposite. A few habits make a big difference:

• Set expectations at sign-up: what you will send and how often.
• Segment your list so people get content that matches their interests.
• Use a sender name people recognise and a subject line that matches what’s inside.
• Make unsubscribing easy. An unsubscribe costs you far less than a spam complaint.
• Send when your audience actually reads. Send-time optimisation, or delivery in each subscriber’s own time zone, helps here.
• Check content before sending. Broken links, a missing plain-text version and image-only emails all count against you.

Your deliverability checklist

• SPF, DKIM and DMARC published and verified for your sending domain
• From address on your own domain, aligned with DKIM
• One-click unsubscribe headers plus a visible unsubscribe link
• Unsubscribes processed within two days
• Spam complaint rate under 0.1%, and never above 0.3%
• Hard bounces kept to a small fraction of each send (well under 2% is a common benchmark)
• Double opt-in on public forms, and no purchased lists
• Suppression list applied to every import
• Inactive contacts re-engaged or removed on a regular schedule
• Google Postmaster Tools set up for your domain
• Spam check and link check run before every campaign