If webmail cannot send, common causes include an incorrect mailbox password, a full quota, invalid DNS, suspended sending due to abuse controls, or a malformed From address.
Common symptoms
- Messages remain in Drafts or fail instantly
- You see SMTP authentication or sender rejected errors
- Only one mailbox is affected
Troubleshooting steps
- Log out of webmail and sign back in to confirm the mailbox password still works.
- Check the mailbox quota and reduce usage if the mailbox is over or near its limit.
- Verify the From address matches the mailbox or an authorized identity.
- Confirm the domain has valid DNS and that outgoing mail is expected to route through the hosting server.
- Send a plain-text test email without attachments to rule out message size or content filtering issues.
Additional notes
- A mailbox can receive mail while still failing to send if authentication or sender policy checks fail.
- Large attachments may exceed outbound limits even when smaller tests work.
When to contact support
Contact support with the full error message if webmail authentication succeeds but outbound sending still fails.