On 9/1/2013 7:04 PM, LuKreme wrote: > On 01 Sep 2013, at 15:35 , Noel Jones <njo...@megan.vbhcs.org> wrote: >> If you want your HELO to be consistent regardless of which IP is >> used, use a separate hostname that points to both A records. >> >> mail.example.com A A.A.A.A >> mail.example.com A B.B.B.B > > Won't this cause a problem with the MX records? They will both point at > mail.example.com and one of those IPs will not be available at any given time.
Yes it will be a problem, for the reason you state. Roman described a dual homed backup architecture. Here he should use two distinct PTR, A, and MX records. If he creates two MX with different priority he should be fine. The one with lower priority (higher value) should be tied to IP/PTR/A records which are 'bound' to public IP B which is routed via the backup ISP link. SMTP clients should only attempt IP B when IP A isn't responding. This is just like the primary/backup MX architecture, but in this case there is only one host on a dual homed backup network, instead of two hosts on the same network or separate networks. -- Stan
