The A Record points your hostname to an IP address. Record A specifies IP address (IPv4) for given host. This is one of the most frequently used records in the DNS Zones. The only parameter is an ipv4 field which is a single IPv4 address in dotted-decimal format. The ipv4 field is an address not a label (name) and therefore is not terminated with a '.' (dot). If hostname is BLANK (or space) then the last valid name (or label) is substituted.
If multiple addresses are defined with the same name then BIND will respond to queries with all the addresses defined but the order may change. Cyclic order is the BIND default but you can control it with the BIND named.conf statement rrset order. The same IP may be defined with different names.
IP addresses do not have to be in the same class or range. IPv4 addresses are reverse mapped using the PTR RR.
In the above example BIND will respond to queries for mail.example.com as follows (assuming you are using the default rrset-order order cyclic):
1st query 192.168.0.15, 192.168.0.32, 192.168.0.3
2nd query 192.168.0.3, 192.168.0.15, 192.168.0.32
3rd query 192.168.0.32, 192.168.0.3, 192.168.0.15
4th query 192.168.0.15, 192.168.0.32, 192.168.0.3