With a single wildcard SSL certificate, you can secure multiple services on different sub-domains without any limits, e.g. a wildcard certificate for *.alpirossl.com will actually secure:
- www.alpirossl.com
- mail.alpirossl.com
- ftp.alpirossl.com
- whatever.alpirossl.com
You can also have a wildcard SSL certificate for other than 2nd-level domain. E.g. if you need to secure anything.sub.alpirossl.com, simply purchase a wildcard SSL certificate for *.sub.alpirossl.com. Or even for *.sub2.sub.alpirossl.com, if you wish. There are no limits.