How Email Delivery Works (Send to Inbox)
Ever wonder what happens between hitting send and the message appearing in an inbox? Understanding the journey makes every deliverability decision clearer.
TL;DR
Your MTA looks up the recipient's MX record, opens an SMTP connection, the receiver runs authentication and reputation checks, then decides inbox, spam or reject. Every step is a place to win or lose deliverability.
Step 1 — Submission
An app or client submits the message to your mail server on port 587/465. Your MTA (e.g. PowerMTA) queues it for delivery.
Step 2 — MX lookup
The MTA queries DNS for the recipient domain's MX record to find which server accepts its mail. (gmail.com's MX points to Google's mail servers, for example.)
Step 3 — SMTP handshake
Your server connects to the recipient's server on port 25 and negotiates the SMTP conversation (HELO/EHLO, STARTTLS, MAIL FROM, RCPT TO, DATA).
Step 4 — Authentication & reputation checks
The receiver verifies SPF, DKIM and DMARC, checks your rDNS, and weighs your IP/domain reputation and the message content.
Step 5 — The placement decision
Based on all signals, the provider routes the message to:
- Inbox — you passed.
- Spam/Junk — authentication or reputation concerns. See how to avoid spam.
- Reject/bounce — hard fail; handled by bounce processing.
Why this matters
Deliverability isn't luck — it's the sum of these checks. Nail authentication, reputation and content and you tilt every decision toward the inbox.
AutoPMTA manages every step of this journey — from MTA to DNS to deliverability. View plans.
Key takeaways
- Delivery = MX lookup → SMTP handshake → checks → placement.
- Receivers verify SPF/DKIM/DMARC, rDNS and reputation.
- Each step is a chance to win or lose the inbox.
- Strong authentication + reputation tilts placement your way.
Frequently asked questions
What is an MX record?+
An MX (Mail Exchange) record is a DNS entry that tells sending servers which mail server accepts email for a domain. The MTA looks it up to know where to deliver a message.
What happens when you send an email?+
Your MTA queues the message, looks up the recipient domain's MX record, opens an SMTP connection, the receiver runs authentication and reputation checks, then decides whether to deliver to inbox, spam, or reject it.
Why do emails go to spam instead of inbox?+
Placement depends on authentication (SPF/DKIM/DMARC), rDNS, IP/domain reputation and content. Weakness in any of these can push a message to the spam folder.