Catch-all

/jabali-panel/mail/catch-all. What happens to mail addressed to a local part that does not exist as a mailbox or forwarder.

Options

• Reject (default): Stalwart returns SMTP 550 5.1.1 User unknown to the sending server. The sender’s MTA generates a bounce. This is the recommended default because it prevents backscatter and signals to legitimate senders that the address is wrong.
• Discard: accept the mail and silently drop it. Useful only when reject is causing legitimate but mistyped mail to bounce (rare); generally discouraged.
• Forward to mailbox: accept and deliver to a designated mailbox. The destination mailbox sees the original To: header so you can route or filter on it.
• Forward to address: accept and forward to an external address. Subject to the same SRS / SPF considerations as ordinary Forwarders.

Per-domain configuration

Catch-all is per-domain. Each domain may have its own setting; the page lists one row per mail-enabled domain in your account.

Spam implications

Catch-all “Forward to mailbox” makes the destination mailbox an easy target for dictionary spam (every typo of a real address lands here). The destination mailbox typically receives orders of magnitude more spam than a normal mailbox. Stalwart’s spam filter applies, but consider the trade-off before enabling.

Recommendation

Default to Reject. Switch to Forward to mailbox only when you have a specific business reason and you accept the spam load.

What about “Reject” plus an autoresponder

Not supported. Reject and autoresponse are mutually exclusive, the SMTP transaction is rejected before the autoresponder could fire. To send a “this address is wrong, please use X” reply automatically, accept into a mailbox + set an autoresponder on that mailbox + redirect / discard the original.