Deliverability determines whether the audience a business worked to build ever sees its emails. A campaign with a perfect subject line is worthless if it lands in spam, which makes deliverability a prerequisite for every other email metric, from open rate to revenue.
What Affects Email Deliverability?
- Authentication: SPF, DKIM, and DMARC records prove the sender is legitimate and not spoofed.
- Sender reputation: mailbox providers score the sending domain and IP based on past behavior; a poor score sends mail to spam.
- Engagement: opens, clicks, and replies signal that recipients want the mail, while deletions without opening signal the opposite.
- Complaints and spam reports: recipients marking mail as spam is one of the strongest negative signals.
- List hygiene: sending to invalid, inactive, or purchased addresses drives bounces and complaints that damage reputation.
What Is Email Authentication?
Authentication is the technical foundation of deliverability. SPF specifies which servers may send mail for your domain. DKIM adds a cryptographic signature that proves a message was not altered in transit. DMARC ties the two together and tells receiving servers what to do with mail that fails. In 2024 Google and Yahoo made authentication mandatory for bulk senders, so SPF, DKIM, and DMARC are now requirements rather than best practices for anyone sending at volume.
What Is Sender Reputation?
Mailbox providers keep a running score of each sending domain and IP based on how recipients react to its mail. Consistent engagement, low complaint rates, and clean lists build a good reputation and reliable inbox placement. A spike in complaints, a burst of sending to a cold list, or a sudden volume increase can damage it quickly, and reputation is far easier to protect than to rebuild.
How Do You Improve Deliverability?
The durable fixes are behavioral, not tricks. Set up SPF, DKIM, and DMARC correctly. Send to people who opted in and remove those who stop engaging. Keep the list clean by pruning invalid and inactive addresses. Warm up a new domain or IP gradually rather than sending at full volume immediately. Make unsubscribing easy, because a visible unsubscribe link generates far less damage than a spam complaint.
Frequently asked questions
What is the difference between delivery and deliverability?+
Delivery means an email reached the recipient's mail server. Deliverability means it reached the inbox rather than the spam folder. An email can be delivered yet filtered into spam, which counts as a deliverability failure.
What are SPF, DKIM, and DMARC?+
They are email authentication standards. SPF lists which servers may send for your domain, DKIM adds a signature proving a message was not altered, and DMARC ties them together and tells receiving servers how to handle failures. Google and Yahoo made them mandatory for bulk senders in 2024.
Why are my emails going to spam?+
Common causes are missing or misconfigured authentication, a poor sender reputation, low engagement, high spam complaints, or sending to invalid and inactive addresses. Fixing authentication and list hygiene, and sending only to engaged recipients, usually resolves it.