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.
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.