Michael,

There isn't currently a feature to remove duplicate messages in SmarterMail.  However, I've gone ahead and submitted this as a feature request for you.

Awesome.

BTW, would also be great to have an auto-archive so emails older than xx days is automatically moved to a year-based folder, both inbox and sent. The last time I manually tried to move emails around like that their indexes got munged and after two attempts I gave up. That was under v15.x, so perhaps this is no longer an issue anymore?

Remove Duplicate Emails and Auto-Archive Emails are two great suggestions that I too would like to see in SmarterMail some day. These would be massive QoL improvements. 

+1

Michael,

If you are using the enterprise edition you can turn on message archiving for specific domains or all domains.  You can then use Folder Auto-Clean to delete messages older than X days from a specific folder.  So if you want them deleted from the inbox and sent items you would need to create a rule for each of those folders.  

As I mentioned, above, I created multiple Sent folders under Archive/Year folders, and moved all emails from Sent to them, based on year (ie; all emails I sent in 2017 went into Archive/2017/Sent) and then ran the de-dupe add-on. Worked like a charm. I guess my Sent folder needs to be re-indexed.

+1