Overview
Outis is an email anti-spam utility that generates a fake user-unknown delivery notification for a message you have already received. Its purpose is to make an unwanted sender believe that the recipient address does not exist, which may help remove the address from automated mailing lists.
The project takes its name from the Greek word for “nobody,” echoing the idea that nobody can be reached at the mailbox.
Key Features
- Builds an RFC 3464 delivery status notification modeled on Postfix.
- Includes a human-readable explanation, a 5.1.1 delivery status, and the original message as an attachment.
- Supports individual email files, clipboard input, and batches of visible files from directories.
- Provides preview, confirmation, dry-run, output-file, account-selection, and post-send deletion options.
- Stores account passwords in the operating system keychain.
Accounts and Message Handling
Each configured account covers one domain. Outis matches an account against recipients found in the original message, allowing the sender identity, mail host, and SMTP server to correspond to that domain. An account can also be selected explicitly when automatic matching is unavailable or ambiguous.
In batch mode, files that cannot be parsed or matched are reported and skipped while processing continues for the remaining inputs. Directories are handled non-recursively and expand to visible regular files regardless of extension.
Requirements and Limitations
A credible bounce requires a domain controlled by the user and, ideally, an SMTP account that permits sending as its mailer-daemon identity. Consumer mail providers may rewrite the sender header and reveal the actual account.
Because Outis responds after the original message has been accepted, it is not equivalent to rejecting mail during the SMTP conversation. The sender may still see the earlier delivery as successful, retries can continue reaching the mailbox, and the effect depends on the sender processing the notification.