> ## Documentation Index
> Fetch the complete documentation index at: https://help.midas.host/llms.txt
> Use this file to discover all available pages before exploring further.

# Fix email bounces

> Resolve common SMTP errors like 550, 553, and 554 with practical steps.

## Common causes

* Recipient doesn’t exist
* Blocked IP or domain reputation
* SPF/DKIM/DMARC failures

## Fixes

1. Verify the address and mailbox quota.
2. Check your DNS records.
3. Send a plain‑text test without links.
4. Contact Support with full headers if persistent.

## Codes

* 550: Mailbox unavailable
* 553: Authentication required
* 554: Transaction failed (policy block)