Improving Email Deliverability

Table of Contents

• Before starting
• Set up email authentication
• Manage sender reputation
• Troubleshoot common problems
• Have more questions?

Most deliverability problems trace back to missing or misconfigured DNS records and poor sender reputation. This guide walks through the changes you can make in DNSimple (and alongside your email provider) to improve inbox placement.

For background on what deliverability is and why it matters, see Understanding Email Deliverability.

Before starting

You will need:

• Access to your domain’s DNS records in DNSimple (or the ability to request changes from whoever manages DNS)
• Access to your email service provider’s settings to retrieve SPF includes, DKIM keys, and DMARC preferences
• A list of every service that sends email on your domain’s behalf (corporate email, transactional, marketing, etc.)

Set up email authentication

Proper authentication is the single most impactful thing you can do for deliverability. Mailbox providers use SPF, DKIM, and DMARC to decide whether incoming mail is legitimate.

Configure SPF

An SPF record tells receiving servers which IPs and services are authorized to send email for your domain.

For full setup details, see Set Up SPF Records.

Configure DKIM

A DKIM record publishes a public key that receiving servers use to verify the cryptographic signature your email provider attaches to each outgoing message.

Repeat this for each service that sends email on your behalf. Each service typically uses its own selector. See Managing Multiple DKIM Selectors if you have more than one.

For full setup details, see Set Up DKIM.

Configure DMARC

A DMARC record tells receiving servers what to do when SPF or DKIM checks fail, and where to send authentication reports.

For alignment requirements between SPF, DKIM, and DMARC, see Understanding SPF, DKIM, and DMARC Alignment.

Manage sender reputation

Even with correct authentication, poor reputation can push your email to spam. Reputation is tied to your domain and sending IP.

Check your current reputation

Use these free tools to assess where you stand:

• Google Postmaster Tools - Gmail-specific reputation, spam rate, and authentication data. Requires domain verification.
• Microsoft SNDS - Outlook/Hotmail IP reputation and complaint data.
• Sender Score - General reputation score (0-100) based on sending history.

Check blacklists

If your domain or sending IP is on a blacklist, deliverability drops significantly:

• Use MXToolbox Blacklist Check to scan multiple blacklists at once.
• If listed, follow the delisting process provided by the blacklist operator. Most require you to fix the underlying issue (e.g., compromised account, spam complaints) and submit a removal request.

Reduce bounce rates

High bounce rates - especially hard bounces - are one of the fastest ways to damage sender reputation.

• Remove hard-bounce addresses from your list immediately. These are permanent failures (invalid address, domain does not exist) that will never succeed.
• Investigate persistent soft bounces (mailbox full, server temporarily unavailable). If an address soft-bounces repeatedly, treat it as a hard bounce.
• Keep your overall bounce rate below 2% and hard bounces below 0.5%.

Reduce spam complaints

Mailbox providers weigh spam complaints heavily. Keep your complaint rate below 0.1%.

• Only send to recipients who opted in.
• Make the unsubscribe link easy to find and honor it immediately.
• If you see a spike in complaints after a specific campaign, review what changed.

Troubleshoot common problems

Emails going to spam despite authentication passing

If SPF, DKIM, and DMARC all pass but email still lands in spam:

1. Check your domain and IP reputation with the tools listed in Check your current reputation.
2. Check blacklist status with MXToolbox.
3. Review email content for spam triggers (excessive images, misleading subject lines, URL shorteners).
4. Verify your DMARC policy is not still set to p=none - some providers treat unenforced DMARC as a weaker signal.

Authentication failing intermittently

If authentication passes for some messages but fails for others:

1. Verify all sending services are included in your SPF record. A forgotten service (e.g., a CRM that sends on your behalf) causes SPF failures for those messages.
2. Check that DKIM is configured for each sending service, not just your primary email provider.
3. Review DMARC aggregate reports to identify which source IPs or services are failing. See Monitoring Email Deliverability for guidance on interpreting reports.

High bounce rates on a new domain

New domains have no sending history, so mailbox providers are cautious:

1. Start with low volume and increase gradually over several weeks.
2. Send to your most engaged recipients first to build positive engagement signals.
3. Ensure authentication is fully configured before sending the first message.

Have more questions?

If you have additional questions or need assistance with improving email deliverability, contact support, and we’ll be happy to help.