So I am slightly puzzled here and maybe someone can clear this up for me if I have missed something. Ok, here's the scenario:

 

A user we host sends an email to someone. Now with my understanding on spam filtering, if a user emails someone the recipient should be added to a whitelist/safelist in SM correct? Reason I ask is because one of the user's brought to my attention that they emailed someone a day or 2 ago. The recipient reply that came back this morning ended up in their Junk E-mail folder on their webmail. Any idea why this happened? Shouldn't the email address they sent the email to in the first place be safe listed for delivery going forward? If not what is the best method that I can go through to make sure automatic white listing for all users starts happening? Is this even possible?

 

Another piece of information, this user is using a mail client and not web mail to send emails. Is this going to be another case where users who use an email client are left out in the cold? Our customers use email clients 99% of the time and only 1% use webmail. So if this is the case where users who use a mail client don't have an email address added to some safe list or white list, then this seriously needs to be added or addressed immediately.