Use the local `sendmail` command if a mail transfer agent is already installed and configured
Install a local MTA such as `postfix` or `exim4` if permitted in the sandbox
Configure the MTA to relay through an internal mail server that does not require authentication
Use an SMTP server on the local network that allows unauthenticated relay from the sandbox IP
Send mail directly to the recipient’s MX server using `mailx`, `sendmail`, or `swaks` if outbound SMTP is allowed
Use `msmtp` with a relay host that accepts anonymous submission from the sandbox
Use `curl` with a local SMTP endpoint if one is available without authentication
Use a trusted internal mail relay or gateway already authorized for the sandbox environment
Use application-level email APIs only if they support unauthenticated local access in the sandbox
Verify outbound port 25, 465, or 587 access is permitted by the sandbox network policy
Check whether the sandbox provides a built-in mail utility or preconfigured relay service
Avoid attempting to bypass authentication on servers that require credentials