smtp bounce code
550 5.1.8Bad sender address
what to do
Keep the address, fix your side
The problem is your From or envelope address, not the recipient.
What the server is telling you
The receiving server rejected your sender address, usually because the domain does not resolve, has no MX, or fails a sender verification callout back to you.
Next steps
- →Do not suppress the recipient.
- →Make sure your sending domain resolves and can receive mail itself.
- →Some servers refuse senders whose domain cannot accept a reply.
Commonly returned by: Postfix, Exim, strict configurations
Find these before you send, not after
Paste a list and see which addresses sit on domains that accept no mail, which are one character from a real inbox, and which are on catch-all domains where nothing can tell you anything. Free, no signup, nothing stored.
Check a list →