Foreign SMTP Domain document - Restrictions tab
Entries on the restrictions tab apply only to servers running the Domino Release 4.x SMTP MTA. Use the Configuration Settings document to restrict the source domains for Domino R5 and later.
FieldEnter
Allow mail only from domainsThe Notes domains that are allowed to send mail to the SMTP destination specified on the Routing tab. Leave this field blank to allow mail from any domain.
Deny mail from domainsThe Notes domains not allowed to send mail to the SMTP destination specified on the Routing tab. Leave this field blank if you do not want to explicitly deny mail from any domains.