Every email we send from Salesforce shows up in our clients, prospects, etc email inboxes with one of these long strings:

 via lw7vxw382z3ooluh.ysr5j3mz574hjqmy.6gjky.e-jcdumao.e.bnc.salesforce.com 

We've received multiple comments about this as it looks suspicious even though it's just a cosmetic issue. Is there any simple fix to this?

Thanks

Has anyone created a code for this? We would like to create a new field that returns the last time a lead, or contact, was called. The problem with the "last activity" field is that it includes mass emails which doesn't really help us. Figure we need to use Apex code to query the type of activity etc. and bring back the date of the last phone call.