Hello, I've been thinking about different ways of load balancing between two SMTP servers via DNS round-robin. I can see at least two different methods.
Method 1 - Single MX record that points to a host that resolves to multiple IP addresses: # Individual SMTP servers local-data: "smtp1.example.com. IN A 10.0.5.51" local-data: "smtp2.example.com. IN A 10.0.5.52" # DNS round-robin for smtp.example.com via multiple A records local-data: "smtp.example.com. IN A 10.0.5.51" local-data: "smtp.example.com. IN A 10.0.5.52" # Single MX record that resolves to multiple IP addresses local-data: "example.com. MX 10 smtp.example.com." Method 2 - Multiple MX records with equal priority that point to hosts that each resolve to a single IP address: # Individual SMTP servers local-data: "smtp1.example.com. IN A 10.0.5.51" local-data: "smtp2.example.com. IN A 10.0.5.52" # Multiple MX records local-data: "example.com. MX 10 smtp1.example.com." local-data: "example.com. MX 10 smtp2.example.com." I think method No 2 is the traditional way of specifying multiple SMTP servers in DNS. Can anyone suggest specific advantages/disadvantages for both methods, or are they functionally the same? PS. I tried using Postfix smtp-source, but it does not seem to support lookup via MX records. So I could only test DNS round-robin: for i in $(seq 1 100) do smtp-source -c -l 10 -s 1 -m 1 -t [email protected] smtp.example.com:25 done This seems to work quite well with 50/50 load distribution. _______________________________________________ Postfix-users mailing list -- [email protected] To unsubscribe send an email to [email protected]
