I just moved my main mail account and web content from a low-cost
(low-quality) provider to my own root server running CentOS 7. I
transferred the domain name from DNS management to my registrar, configured BIND, Apache, Postfix, Dovecot, NTP, SELinux, etc. Now things are running rather nicely. One thing is puzzling me though.
The updated mail server DNS seems to have spread around so far.
$ host -t mx microlinux.fr microlinux.fr mail is handled by 10 mail.microlinux.fr.
Unfortunately, some hosts seem to still keep the old DNS information, which was:
$ host -t mx microlinux.fr microlinux.fr mail is handled by 10 mx1.nfrance.com.
In your experience, what’s the “longest” a DNS cache is configured to keep outdated information? A day? A week? A month? Longer?