Restricting sending mail to domain or group

[admin]

Am Mittwoch, den 05.12.2018, 22:31 +0000 schrieb Jochen Bern:
> On 12/05/2018 06:57 PM, admin (@awib.it) wrote:
> > I have a group alias (all at company.com).
> > (1) Only company.com accounts should be able to send an email to
> >     everybody in that company via all at company.com.
> 
> Do you have a means to identify "some suitable account was used" - as
> opposed to a trivially forged sender address - *other* than by
> watching
> the actual MUA-to-MSA login happen?

Either way would suffice - the simpler the better.

Restricting the sender to be on the same domain if mail is sent to the
company group alias would be fine.

All I try to achieve is to protect those in the group from unwanted
"SPAM", so no one from outside the domain should be able to send to 
that alias (all at company.com is quite generic...).
Optionally only chosen senders (whitelist) should be able to send to 
that alias. We do not want our mail system to become a craigslist or 
everbody being able to reach thousdands of people with only one email
being sent.

We are rather generous thinking of mail attachments (up to 100MB).
I do not want to see an email like this copied over to thousands of
accounts...


>  [...]
> 
> Regards,

Thanks four your thoughts!

-M