A lot of them will let you if you ask, for instance even ionos or ovh. Digital ocean have a blanket ban on port 25 ipv6 but I haven't seen a reason to use them

A lot of them will let you if you ask, for instance even ionos or ovh. Digital ocean have a blanket ban on port 25 ipv6 but I haven't seen a reason to use them for a decade now. +1 for mythic beasts