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
They are quite expensive for some ranges of storage which you might need for IMAP if you need a lot less than where the HDD pricing starts.
On the other hand HDD is fine for a mail server and you can get 400Gb for not much more than some email providers will charge you for three 10Gb mailboxes.