Hello all, First, I hope this is not off-topic for NANOG, please be gentle with me as this is my first post. I would be most interested to hear NANOG theories on the variety of MX record practices out there, namely, how come there seem to be so many ways employed to achieve the same goal ? Do you have experience in more than one of these methods and which do you favour ? To illustrate my question : (1) If you query the MX records for, Hotmail or AOL you will receive 4 equal weight MX records, each of the MX records having a round-robin set of IPs. e.g. hotmail.com. 2706 IN MX 5 mx4.hotmail.com. hotmail.com. 2706 IN MX 5 mx1.hotmail.com. hotmail.com. 2706 IN MX 5 mx2.hotmail.com. hotmail.com. 2706 IN MX 5 mx3.hotmail.com. -and- mx3.hotmail.com. 1926 IN A 65.xxxxxxx mx3.hotmail.com. 1926 IN A 65.xxxxxxx mx3.hotmail.com. 1926 IN A 65.xxxxxxx etc.etc. (2) Alternatively, some people, particularly the ones that use hosted filtering, tend to have one MX record, which as multiple round robin IPs. e.g. microsoft.com. 780 IN MX 10 mail.global.frontbridge.com. -and- mail.global.frontbridge.com. 1728 IN A 65.xxxxxxx mail.global.frontbridge.com. 1728 IN A 207.xxxxxxx etc. etc. (3) And others simply have a more traditional setup using multiple MX records and only one IP per MX record with no round robin apple.com. 931 IN MX 10 mail-in14.apple.com. apple.com. 931 IN MX 20 mail-in3.apple.com. apple.com. 931 IN MX 20 eg-mail-in2.apple.com. etc.etc. So what's the big deal ? Please note I'm not asking which is "better" ... I am just curious and interested to hear your professional opinions and experiences. Personally, I favour the simple option 3, multiple MX records. Thanks y'all.