SENDERCHECK

Check if the sender (envelope "mail from:") of a message really exists (in the LDAP directory). If not give a 550 reject right now.

Default:

off

Affects:

qmail-smtpd

Example:

"" or "LOOSE" or "STRICT"

Note:

Only applies to senders whose domain is listed in ~control/locals.
Everything else is assumed to be an external message with a foreign sender coming in, so no check applied. This is normal mode.
Setting to "LOOSE" will allow only senders which are listed either in ~control/locals or ~control/rcpthosts.
Setting to "STRICT" will only allow senders which are listed in ~control/locals. With this you can enforce for example that people from certain ip ranges can only send if they have a valid existing email address with you.
Addresses or domains listed in ~control/goodmailaddr are unconditionally allowed in all cases.