A Simplified Flow from Sender to Receiver

Billions of emails are sent daily, and each one will follow the same path from the sender to the receiver:

The SMTP Handshake

For every email address you send to, you initiate a SMTP, or Simple Mail Transfer Protocol, handshake. This is where the SMTP recognizes the domain you're sending to, contacts the receiving server responsible for accepting messages for that domain, and they exchange multiple pieces of information.

The Domain Name System

The DNS works like the phone book of the internet. When the email has been sent, the receiving server checks to find out who the sender is.


Authenticating an email verifies that the email message actually came from the sender listed in the 'from' field in the email's header, and covers the Mail From domain, and ensures that the email hasn't been maliciously altered in transit.


Deliverability success is largely down to your sender reputation. The better your reputation is, the more likely it is that your email will land in your recipient's inbox. Reputation is complex, and determined by a number of factors:

  • Recipient engagement: Creating an email is only half of the battle - encouraging your recipients to open, read, and click on your CTAs is the other half!

  • Email content: What's actually in your email directly affects your sender reputation. Build a good reputation with well designed emails, the right balance of text and image, and legitimate and enticing links to direct recipients to your website.

  • Spam complaints: The last thing you want is for your email to be reported as spam, as this can really damage your sender reputation. Learn what to avoid here.

  • Spam traps: Sending emails to a spam trap can be bad news: avoid this by periodically removing inactive Profiles from your mailing lists, and always use Double Opt-in in your sign-up process.

  • Invalid email addresses: Sending emails to invalid addresses will result in bounces, and too many bounces can ultimately harm your sender reputation.

  • Blacklists: Maintaining good consent list hygiene is essential to avoid being blacklisted: anything from sending bulk emails to spam traps, to a single bad email can cause your server or domain to be blacklisted.

  • Domain Reputation: A good sender domain and From-domain reputation comes with time and patience: continue to send good emails with high levels of engagement and avoid spam complaints, and your recipient's ISP will automatically place your email in the Inbox folder - and this is where we want to be!

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