Explicit priority MX with only AAAA record

[Steve Bertrand]

Hi everyone,

I can't really come up with a conclusive answer to hopefully a simple 
question.

Currently, I have an MX for smtp.ibctech.ca. This name holds both an A, 
and an AAAA record.

I've been considering breaking that, and having separate explicit MX 
records for each an A and an AAAA record, and setting the IPv6 MX as 
priority, the v4 as next priority.

Before I go test this on the one MX box I have and possibly cause myself 
grief, does anyone know if there will be negative effects for v4 only 
clients?

Things work fine the way they currently are, but I'm worried that with 
MX records, clients following standard procedures may not be able to get 
around an MX with no A record.

Regards,

Steve