Message Acceptance
Whether the receiving system accepts the SMTP transfer — distinct from where the message is filed afterward.
- Reading time:
- 5 min
- Difficulty:
- Intermediate
- Estimated duration:
- 5 min
- Prerequisites:
- None
- Last updated:
- 2026-07-15
- Author:
- empire
Definition
Message acceptance is the SMTP-layer decision to take responsibility for a message (typically a 2xx response) versus deferring or rejecting it.
Why it matters
Separate transfer failures from inbox-placement problems so operators diagnose the right layer.
How it works
During the SMTP session the receiver may accept, defer (4xx), or reject (5xx) based on reputation, authentication, policy, and load. Accepted mail can still be filed to junk later.
Limitations
- Acceptance rates alone do not describe user-visible placement.
Common misconceptions
- If SMTP says 250, deliverability is solved.
How to verify
- Capture SMTP response codes from your MTA or ESP logs.
- Classify hard rejects versus temporary deferrals.