Not sure what version of Smarter Mail you are using.

We are using Version 14.

In 14, If you are a domain administrator, it looks like you can go into "settings" then "Domain Settings" and under "Filtering" go to "Content Filtering"  

There you can set up a filter that says :

From Address (From a specific domain)

Click Next

"From Address"  "Does Not Match" (type in your domain) - 

click Next

Give the Filter a Name

Click "Prefix Subject"  and maybe use "{External Email}"  or something

Click Save.

That should do it, but I have not tested this

Thanks Curtis

This Helps. I am using SM 16x, and am able to prefix the subject of the email message with desired text. 

The examples I saw allowed for the body (Top) of the email message. It had a bit more of an effect as they could make it red and Bold font. Also more space to work with messaging.

If I cannot get in the body of the email then this will be my option.

Thanks

Any other responses to this, I am seeing more servers showing these messages with color for impact.

Hello and good afternoon. I was not able to find a way to accomplish this, and I'd like to suggest this to our development team as a feature request. I've now submitted this to them for consideration in the future. In the meantime please use the solution provided by Curtis. Thanks for submitting this great idea!

Thanks Kyle !

Personally I would like to see this set up for multiple uses.

- Per domain

- Whole server

This could be VERY useful for a few reasons 

Yes, to warn people about potential SPAM and scams. Also, if there is some type of imminent date (server move, maintenance, corporate reminders, etc) that people need to be reminded of over and over.  Maybe be able to custom configure each attached message, basically, to work like a signature, but a prefix on the inbound email.

This could also interact with the SPAM settings too. Like when receiving an email from a new domains that are less than 30 days old ?

And if the email is spoofed, where it says it came from your domain, but it obviously came from an outside source.

So,  i just was looking for something else, and see this has been talked about before.

and

What ever happened with this feature request?

And it's not as simple as the current content filter allows. The check must work something like this:

IF email FROM domain = TO domain

AND domain is LOCAL to SM

AND (SMTPAUTH IS FALSE AND SENDING IP <> WHITELISTED)

THEN PREFIX SUBJECT {EXTERNAL EMAIL}