reverse dns configuration for IPV4, IPV6+ dns+ mail ?

[Pierre Couderc]

Well, we have 2 computers in xxx.com subnet provided by ISP on 123.124.125.126 ipV4  address and corresponding IPV6 segment

mail.xxx.com :    2a01:e34:xxxx:xxxx:xxxx:xxxx:1122:3344 for mail server
ns.xxx.com :  2a01:e34:xxxx:xxxx:xxxx:xxxx:aabb:ccdd for dns server

In xxx.com bind :

mail A 123.124.125.126
mail AAAA 2a01:e34:xxxx:xxxx:xxxx:xxxx:1122:3344

ns A 123.124.125.126
ns AAAA 2a01:e34:xxxx:xxxx:xxxx:xxxx:aabb:ccdd

What should I put for IPV4 reverse address : if I put mail.xxx.com, the reverse address will not point on ns.xxx.com, and if put ns.xxx.com, the reverse dns will not point on mail.xxx.com, and I shall have mail problem.

What are the best practices fore thus problem ?

Thanks
PC