Email Deliverability Explained: Why Your Emails Sometimes Land in Spam

You compose an important email, hit send, and wait. The recipient says they never received it. Or worse — they find it in their spam folder three days later. Email delivery failure is one of the most frustrating experiences in digital communication, and it happens more often than most people realise.

Understanding how email delivery works — and why it sometimes fails — empowers you to make better choices about the email services you use.

How Email Delivery Actually Works

When you hit send on an email, the message does not travel directly to the recipient's inbox. It goes on a multi-step journey:

1. Your email client submits the message to your email provider's sending server.
2. The sending server looks up the recipient domain's mail exchanger (MX) records via DNS to identify where to deliver the message.
3. The message is transmitted to the recipient's incoming mail server via SMTP.
4. The recipient's server runs filtering checks — spam detection, authentication verification, reputation scoring — before deciding whether to deliver the message to the inbox, route it to spam, or reject it entirely.

The Authentication Standards: SPF, DKIM, and DMARC

The three most important technical standards in email deliverability are authentication protocols that verify that an email claiming to be from a particular domain actually originated from an authorised sending server:

SPF (Sender Policy Framework)

SPF is a DNS record that specifies which IP addresses are authorised to send email on behalf of your domain. When a receiving server gets an email from your domain, it checks the SPF record to confirm the sending server is on the approved list. If it is not, the email may be rejected or marked as suspicious.

DKIM (DomainKeys Identified Mail)

DKIM adds a cryptographic signature to every outgoing email, signed with a private key that only your mail server holds. The corresponding public key is published in your DNS records. Receiving servers verify the signature against the public key to confirm the message has not been tampered with in transit.

DMARC (Domain-based Message Authentication, Reporting & Conformance)

DMARC ties SPF and DKIM together and tells receiving servers what to do if authentication fails: quarantine the message (send to spam), reject it outright, or take no action but send a report. DMARC also enables domain owners to receive reports about who is sending email from their domain.

Why Sender Reputation Matters

Beyond authentication, every sending domain and IP address has a reputation score maintained by email providers and anti-spam networks. This score is influenced by:

• Spam complaint rates — how often recipients mark emails from your domain as spam.
• Bounce rates — how many emails are undeliverable (often due to invalid addresses).
• Volume patterns — sudden spikes in sending volume from a previously quiet domain trigger suspicion.
• Content signals — certain phrases, excessive links, or unusual formatting patterns that resemble known spam.

How Sendora Ensures Your Emails Are Delivered

Sendora's email infrastructure is designed for maximum deliverability:

• SPF, DKIM, and DMARC are configured correctly for all Sendora domains, providing authentication signals that receiving servers trust.
• Dedicated sending infrastructure maintains a clean IP reputation separate from the broader sending pool of generic email hosting providers.
• Resend integration for transactional email ensures the highest-priority messages — account notifications, verification emails, and system messages — are routed through infrastructure optimised specifically for inbox placement.
• Active monitoring of spam complaint rates and bounce rates ensures that Sendora's sending reputation remains at the highest tier.

What You Can Do to Improve Your Deliverability

If you are using a custom domain with Sendora, here are the most important steps:

1. Follow Sendora's guided setup to configure SPF, DKIM, and DMARC records in your domain's DNS.
2. Warm up your domain gradually if you are beginning to send from a new custom domain.
3. Keep your contact list clean — regularly remove addresses that bounce.
4. Never use email for purposes that could result in spam complaints.

Sendora's setup wizard walks you through every DNS configuration step with clear instructions for all major domain registrars. Proper authentication is the single most effective thing you can do to ensure your emails reach their destination.