Why is my email bouncing?
A "Mail delivery failed: returning message to sender" error means your outgoing email could not be delivered to the recipient's mail server. Here are the most common causes and how to fix them.
1. The recipient's address is wrong
Double-check the email address you're sending to. A single typo will cause an immediate bounce. The bounce message usually includes the address that failed.
2. The recipient's mailbox is full
If the person you're emailing has exceeded their mailbox quota, your message will bounce back. Try contacting them another way.
3. Your IP is on a blacklist
If you've sent a large volume of email recently or your account was compromised, your server's IP may have been added to a spam blacklist. Check your IP at MXToolbox. If you're listed, open a support ticket and we'll help get it resolved.
4. SPF or DKIM is misconfigured
SPF and DKIM records tell receiving mail servers that your email is legitimate. Log into cPanel and go to Email → Email Deliverability to check and repair your records automatically.
5. The recipient's server is blocking you
Some mail servers have strict filtering rules. The bounce message will usually include a reason code. If it says "550" or mentions spam policy, the block is on their end.
Still stuck?
Open a support ticket and paste the full bounce message. The error codes tell us exactly what's happening and we'll get it sorted quickly.
