Can I use an A record instead of an MX record?

> I have a single machine running DNS mail and web for a domain
> and I'm not sure that I have DNS setup properly. If the machine
> that is running the mail is the name of the domain does there need
> to be an MX record for mail?

Technically, no. Nearly all mailers will look up A records for a
domain name in a mail destination if no MX records exist.

> If an MX record is not needed, how would you put in an MX
> record for a backup mailserver.

You can't. If you want to use a backup mailer, you need to use
MX records.

> www cname 192.168.0.1
> mail cname 192.168.0.1
> pop cname 192.168.0.1
> smtp cname 192.168.0.1

These CNAME records are all incorrect. CNAME records create
an alias from one domain name to another, so the field after "CNAME"
must contain a domain name, not an IP address. For example:
www CNAME foo.example.

cricket