Why email deliverability matters and how to make sure your emails hit the inbox

Email deliverability is whether your emails reach the inbox instead of the spam folder or nowhere at all. It matters because an email nobody sees can't close a deal, confirm an order or reset a password. To make sure your emails hit the inbox, authenticate your domain with SPF, DKIM and DMARC, email only people who expect to hear from you, remove addresses that bounce, keep spam complaints very low and make every email worth opening.

What is the difference between delivery and deliverability?

Email delivery is the trip from "send" to the receiving mail server. A message is delivered when that server accepts it. Speed matters here: how long it takes from clicking send to the message arriving.

Email deliverability goes further. It is about where the message lands once it is accepted: the inbox, the spam folder or a promotions tab. It depends on your sender reputation, how clean your list is and whether you prove who you are with authentication.

An email can be delivered and still never be seen. That is why sales and marketing teams should track both.

Why do delivery speed and deliverability matter?

A late proposal can lose the deal. Say a prospect asks several vendors for pricing and reviews the proposals in their inbox on Friday afternoon. If yours arrives late or lands in spam, you are not in the comparison.

Customers rely on your emails to use your product. Password resets, sign-in codes, licence keys and invoices are transactional emails. When they arrive late or go to spam, customers contact support instead. One delayed email is a nuisance. Hundreds a day overwhelm a support team.

Slow or missing email costs you revenue, your support team's time or both.

What do Gmail, Yahoo and Outlook require from senders?

The large mailbox providers have tightened their rules. Google and Yahoo started enforcing new requirements in February 2024, and Microsoft followed for Outlook.com in May 2025.

Google adds that you should aim to keep your spam rate in Postmaster Tools below 0.10% and never reach 0.30%. All senders to Gmail also need valid forward and reverse DNS records and a TLS connection. Microsoft says messages from high-volume domains that don't meet its requirements are rejected with error 550 5.7.515.

How do you set up SPF, DKIM and DMARC?

These three DNS records prove to receiving servers that you are allowed to send email for your domain:

• SPF lists the servers and services allowed to send email for your domain.
• DKIM adds a digital signature to each email, so the receiver can check it wasn't changed and really comes from your domain. Google asks for keys of at least 1024 bits and recommends 2048 bits where possible.
• DMARC tells receivers what to do when a message fails SPF and DKIM, and sends you reports about who is sending email in your name. DMARC is now an IETF Proposed Standard, published as RFC 9989, which replaced the older RFC 7489.

Set up SPF and DKIM for every tool that sends email for you, such as your CRM, marketing platform, sales engagement tool and help desk. Then publish DMARC with p=none, read the reports and, once all legitimate email passes, move to p=quarantine or p=reject.

How do you reduce bounces?

A bounce is an email that comes back undelivered. A soft bounce is temporary, for example a full mailbox. A hard bounce is permanent: the address doesn't exist. Hard bounces hurt your reputation most, so remove those addresses straight away.

To keep your list clean:

• Never buy email lists. Google's sender guidelines say plainly not to purchase email addresses from other companies. Bought lists are full of invalid addresses and people who never asked to hear from you.
• Use opt-in. Grow your list through sign-up forms, events, content downloads and product sign-ups. Read more about opt-in.
• Verify addresses before a first send, especially for sales prospecting lists.
• Remove inactive contacts who haven't engaged in a long time, or try one re-engagement email first.

For cold outreach, know the law in the places you send to. In the US, the FTC's CAN-SPAM guide requires honest headers and subject lines, a valid postal address and a clear way to opt out, honored within 10 business days. In the EU and UK, GDPR and ePrivacy rules apply. See our CAN-SPAM entry.

How does sender reputation affect deliverability?

Mailbox providers judge your email partly on reputation: that of your sending domain and of the IP addresses you send from. It is built from how recipients respond, such as spam complaints, bounces and engagement. A bad reputation can also land you on a blacklist. Read more about sender score.

Ways to protect it:

• Choose shared or dedicated IPs carefully. Most businesses send through their email provider's shared IP pools, where reputation depends partly on the provider's other customers. A dedicated IP gives you full control, but only makes sense at high, steady volume, and you must monitor it yourself.
• Ramp up slowly. Google advises starting with a low volume to engaged users and increasing slowly, and warns against sudden spikes.
• Separate email types. Google recommends not mixing promotions into receipts and using a consistent From address for each type. Many companies send marketing email from a subdomain so it can't drag down transactional email.

How do you keep spam complaints low?

Every time someone clicks "report spam", your reputation suffers. Keep complaints low by:

• emailing only people who expect to hear from you
• making unsubscribing easy, with one-click unsubscribe and a visible link
• sending at a frequency people agreed to
• writing subject lines that match the content

The best way to lower complaints is to add value. Personalize based on what you know about the recipient's role and company, answer a real question, share something useful and make the next step clear. Valuable emails get replies, and replies help reputation. See our cold email tips that don't work for what to avoid.

How do you measure deliverability?

Watch these numbers for every campaign and sending domain:

• bounce rate, split into hard and soft bounces
• spam complaint rate, from Google Postmaster Tools and your email platform
• replies and clicks, which show real engagement

Be careful with open rates. Apple's Mail Privacy Protection downloads remote content privately in the background, so emails can be counted as opened even when nobody read them. Read more about email analytics for B2B campaigns and browse email marketing tools.

Email deliverability checklist

1. SPF and DKIM set up for every service that sends email for your domain
2. DMARC published and its reports reviewed
3. One-click unsubscribe and a visible unsubscribe link in marketing email
4. No bought lists, addresses verified, hard bounces removed
5. Spam rate below 0.10% in Google Postmaster Tools
6. Transactional and marketing email separated
7. Volume increased gradually
8. Every email useful to the person who gets it