
IPv6 at LinkedIn Part I - samber
https://engineering.linkedin.com/blog/2016/07/ipv6-at-linkedin-part-i--chippin-away-at-ipv4
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aexaey
Well done for first steps. Even (one of) mail servers' IPv6 record has a valid
reverse record, very nice!

Now, how about adding reverse to the main AAAA too?

Also, what's up with one of MX'es lacking IPv6 address? With both
_mail.linkedin.com_ and _mail-c.linkedin.com_ having the same priority (10),
that's a recipe for 50% of delivery attempts randomly failing to IPv4.

    
    
      $ dig +short aaaa linkedin.com
      2620:109:c002::6cae:a0a
    
      $ dig +short -x 2620:109:c002::6cae:a0a
      (no reply)
    
      $ dig +short mx linkedin.com
      10 mail-c.linkedin.com.
      10 mail.linkedin.com.
    
      $ for i in mail.linkedin.com. mail-c.linkedin.com.; \
        do echo $i; dig +short aaaa $i; done
      mail.linkedin.com.
      (no reply)
      mail-c.linkedin.com.
      2620:109:c006:104::215
    
      $ dig +short -x 2620:109:c006:104::215
      mail-c.linkedin.com.

