Email error 554 5.7.1: Transaction failed: service unavailable or blocked

What it means

A general refusal. The server stopped the delivery for a reason that usually appears in the text after the code, such as a blocked sender, a listed IP or a content rule.

Common causes

• The sending IP is on a blocklist the recipient uses.
• The message was flagged as spam or contains a blocked link.
• The recipient server does not accept mail from your region or network.
• Too many messages were sent in a short time.

How to fix it

1. Read the full bounce text and follow any link it gives.
2. Check blocklists for your sending IP and domain.
3. Remove suspicious links and shorten the message, then test again.
4. Slow down and send fewer messages at a time.

How to prevent it

Most bounces come from addresses that were never checked. Verify each address before you send: syntax, domain, mailbox and risk are checked without sending a message. Test a single address with the free email checker or upload a whole list for bulk verification.

Verify an email address free · Clean a whole list · MX lookup · SPF, DKIM and DMARC checker

Frequently asked questions

What is the difference between 550 and 554?

Both are permanent. 550 often points to the mailbox or policy, 554 is a broader transaction failure.

Is the mailbox bad?

Not necessarily. Many 554 errors are about the sender.

Other error codes

All email error codes