Transferring to a new server

About a week before you move, change the TTL on your DNS record fr the domain to something like 300.
TTL is "Time To Live" in seconds. It's the amount of time a properly configured dns server waits before refreshing your domain record.

By setting your propagation time to 300 seconds (5 minutes). You practically eliminate your dns down time. Most DNS servers/web hosts are familiar with the practice and won't squawk provided you return your dns record to it's original setting (usually 7200/14400) afterwards so they don't waste bandwidth. They probably would squawk if you set it to 60 seconds though.

For some god-forsaken reason though, some mail servers seem to be slower on catching up on dns changes. So you frequently get in a situation where some email sent to the domain goes to host A shile some goes to host B even though the domain resolves to Host B.

The work-around for that situation is to have your email accounts set up on both hosts before the transfer but have both email accounts forward to a 3rd party email account - e.g. googlemail for two or three days. After that, you can turn off the email forwards and drop Host A.

I find that new .org domains typically take longer to propagate than any other new TLD. New .com's and .nets take about 15 minutes. New .orgs take a couple of days. They also take longer
to get the email straightened out.
Be sure to lock the forum db during the transition.

I ran into the same situation when trying to mve my site to a new server.  I used ot use phpbb, but because of the trouble I chose to go with the comunity offered by groupee.com because it is hosted o their server and you just point a subdomain to their server.  fter doing that, when you change servers you just have to update the subdomain settings.

Anyway, what I did originally was use the dedicated IP that I was given for the new server to set everything up prior to the DNS changes taking place.  It worked pretty well and only required some minor mods to the backend after the move to get rid of the references to the IP.

Good luck.