Moving Mail Server to another location / IP address?

[Brian Willoughby]

Good suggestion, but you shouldn't have to wait 48 hours for DNS  
changes that are planned in advance.
My ISP set my DNS timeouts to just a couple of hours, and they made  
this change about three days before the move.  After three days,  
every cached DNS record for my site had a TTL of only a couple of  
hours.  This increases the demand on the system, but it's a fine  
tradeoff for a short term.  When my ip address was updated in the  
primary DNS entry, the whole world knew about it within a couple of  
hours.  Once we were certain the entire transition wasn't suffering  
from some kind of problem, the TTL was modified from a couple of  
hours to a couple of days, thus putting things back to normal.  All  
this requires is a few days advance notice of your move, and a  
professional ISP / DNS hosting.

My info may be out of date, but 48 hours seems short.  I thought the  
typical TTL was 3 days.  I guess the fact is that it is up to the  
person running your DNS.  I scanned the O'Reilly "DNS and BIND" book,  
but found no mention of a "typical" TTL.  But I did find that they  
recommend the practice described above of reducing the TTL ahead of  
time so that the move is completed faster.

Brian Willoughby
Sound Consulting



On Feb 9, 2007, at 12:39, listreader at pvision.co.uk wrote:
If you're beholden to an ISP for any DNS changes I'd make them on a  
Tuesday or Wednesday so that you can chase them in 48 hours if things  
go pear-shaped. I've done changes on a Friday before now and the ISP  
has got the changes wrong. If that happens you have to wait 48 hours  
to contact the ISP (Saturday, Sunday) and then wait another 48 for  
the changes to propagate