Imagine could get away with running this on 1G with light usage/load? Also don't see webmail here, but imagine shouldn't be too difficult to add (I don't have much exposure to the OpenBSD landscape).
https://www.openwall.com/lists/oss-security/2018/07/26/2
https://www.openwall.com/lists/oss-security/2018/03/17/2