Restrict External mails from the Portal server.

Hello,

I have configured SMTP server to send email form Portal.The mails required to be send is related to Self User registration,Forgot Password and User delete, unlock etc.

SMTP server can send mails to all External mail Id's.

However the requiremnt is to restrict the mails to every external Id's while sending to only internal email id's.

How can the email Id be restricted to external Id's from Portal?

Regards,

Am