I proposed an idea past one of the devs recently about being able to populate Trusted Senders automatically when a user sends an email through SM no matter what method they use, so this would include POP, IMAP, mobile devices, etc. The contacts feature implemented in SM16 as trusted senders is nice, but as previously stated in that thread already, I am in the same boat where not all of my users save their contact books in SmarterMail nor do they seem to be interested in doing so. Users want simplicity and trying to change that is often a huge challenge.
The feedback I get from a lot of my users is that they would like to be able to send a user an email and be able to get a response back without the message showing up in their Junk E-mail. I agree with that and I have experienced that situation myself where a response shows up in my Junk E-mail after I sent an email to someone. There was a product we were using in the past that when a user sent an email through the mail server it logged the recipient's email address in a trusted list with the assumption that the sender wanted to get a response back from them. Yes there were pluses and minuses to this method, but it made support calls for this type of complaint to almost none. All my users want is to simply be able to send an email to someone and make sure that when the recipient responds back, the original sender will get it delivered to their inbox. Not having to be concerned with checking their Junk E-mail folder for a response from someone they sent an email to takes the frustration out of the picture. About 99% of my users use email clients and not all of them use Outlook. Out of those users, about 98% - 99% use POP only. So while IMAP would make checking the Junk E-mail folder easier, I don't want to force my users to use IMAP just for that purpose. Giving the user a choice tends to make them happy.
It would be really nice if we could have a feature that we could enable in SM somewhere for people that want to use an automatic method for safe listing ( or adding an entry to a user's Trusted Senders list if it didn't exist already) and for the people that don't care to use that feature, they don't need to have it enabled. That way we cover just about any configuration possible and the mail administrator has a choice how they want to run their server. This type of feature could make it so no matter what method a user has at their disposal to send email through your server, the recipient could be trusted to send an email back without being penalized. This would cover anyone's device/configuration and not just assume all users are just going to use the webmail interface. Giving a user the choice of what they can use at their disposal and having simplicity tends to keep your users / customers happy.