The email should have a spambox or spam/junk folder by default and Spamassassin if enabled should automatically move stuff to it vs flagging it as spam and leaving it in your main inbox. This is comparable to how cPanel's Spambox and every other provider's email is.
For new user adoption having control of the spam filters and having it auto learn from SpamAssassin would be a huge selling point. Rainloop is gorgeous but dealing with spam is never fun.
The guide below is great but the average person may be a tad overwhelmed if not a sysadmin.https://blog.cyberpanel.net/2019/04/18/filtering-spam-in-rainloop-autoreply-and-email-filters-with-sieve/
If this was set up by default or able to be enabled via the control panel that would be sweet.