Disable sending email for users

I’m using mail-in-a-box to give clients access to the addresses that were used to set up accounts on a variety of sites, the problem is these clients tend to be… less than careful with passwords and then inboxes can become compromised.

The best solution here is that once we hand these addresses off to clients, they won’t need to send emails, only receive them. Is there a way to configure per-user blocking on the SMTP level?

Thanks

There is no official way to do that. However you can login them into Outlook but never give them the password in doing so.