🚀 First 100 Signups Get 10K Free Credits and Founder Badge!

Claim Yours Now!
VitaMail

Menu

Email Bounce Codes Guide: SMTP Error Codes

Royal Imanli
Royal Imanli10.27.2025
Share on:
Email Bounce Codes Guide: SMTP Error Codes
Share on:

Frequently Asked Questions

Find answers to common questions about email verification.

What is an SMTP bounce code?
An SMTP bounce code is a numeric message returned by a mail server when an email cannot be delivered. It helps identify the reason for the delivery failure if it’s temporary or permanent.
What does SMTP 550 mean?
The 550 error means the recipient’s server rejected the email. This usually happens when the email address doesn’t exist, your domain is blacklisted, or authentication fails.
What does SMTP 421 mean?
The 421 error is a temporary failure. It often occurs when the recipient’s mail server is busy, overloaded, or temporarily unavailable. The message might be retried later.
What does SMTP 554 mean?
The 554 error typically indicates a permanent failure. It can be caused by spam filters, policy rejections, or the message being flagged as harmful or suspicious.
How do bounce codes affect email deliverability?
Frequent bounces can harm your sender reputation and lower future deliverability. Monitoring and cleaning your email lists regularly helps maintain a strong sender score.

More blogs like this:

How Domain Age Affects Your Email Reputation

How Domain Age Affects Your Email Reputation

Understand the critical link between your domain's age and its email reputation to overcome deliverability hurdles.

Monday, October 20, 2025

Read more
Understanding the Role of AI in Subject Lines

Understanding the Role of AI in Subject Lines

AI takes the guesswork out of email marketing. Learn how smart subject lines increase opens, clicks, and engagement effortlessly.

Monday, October 13, 2025

Read more
How to Write a Welcome Email Series That Converts (with a little help from AI)

How to Write a Welcome Email Series That Converts (with a little help from AI)

Turn new subscribers into loyal customers. Learn how to write a high-converting welcome email series with our proven 3-step framework and smart AI tools.

Monday, October 13, 2025

Read more
Stay Ahead in Email Marketing

Join marketers who get fresh strategies, growth ideas, and new feature updates — only the useful stuff, no spam.

keyboard