> One feature i need is a configurable sub-adressing separator (not just "+").
After years of training my family to use "U-C@D" to help identify where spam is coming from (because there's still an astonishing number of sites that refuse '+' as a valid email character), I realised I'd trapped myself into (probably) having to provide the email server forever because I've yet to find a hosted alternative that provides configurable/additional subaddseps.