How Email Delivery Actually Works

The Lifecycle of an Email

When you click "Send" in Senddera, a complex chain of events is triggered. Here is how it works step-by-step:

1. Queueing

Senddera doesn't send the email immediately. Instead, it creates a "Job" in the Redis queue. This allows the application to remain fast and responsive while workers handle the actual sending in the background.

2. MTA Handoff

A queue worker picks up the job and hands the email data to your configured Mail Transfer Agent (MTA) or sending service (like Amazon SES or your own SMTP relay).

3. SMTP Conversation

Your MTA initiates an SMTP (Simple Mail Transfer Protocol) handshake with the recipient's mail server. During this phase, several things happen:

• DNS Lookup: Your server looks up the MX (Mail Exchange) records for the recipient's domain to find where to send the email.
• EHLO/HELO: Your server identifies itself.
• TLS Negotiation: If possible, the connection is encrypted via TLS.

4. Authentication Checks

The recipient's server performs authentication checks to verify that you are who you say you are:

• SPF (Sender Policy Framework): Checks if the sending IP is authorized to send for your domain.
• DKIM (DomainKeys Identified Mail): Verifies the digital signature attached to the email.
• DMARC: Tells the server what to do if SPF or DKIM fails.

5. Delivery or Bounce

If all checks pass and the recipient's mailbox is active, the email is delivered. If the mailbox is full or doesn't exist, a "Bounce" message is sent back to your server, which Senddera tracks via webhooks.