Quoting Xavier (balug-talk@xav.to):
Further, with decent control over DNS, the timeouts can be decreased a day or two before the transition, which would nearly make future transitions smooth.
It helps, but (just in case you didn't know) there is an annoyingly large amount of caching DNS out on the Net that ignores TTL. Plan for some laggards to take up to about 3 days to catch up, even if you reduce TTL well in advance.
List addresses like: admin@lists.balug.org announcement@lists.balug.org
announce@lists.balug.org
talk@lists.balug.org ..are almost delightful to read IMHO.
Beware of namespace collisions with site-administrative addresses that exist for other purposes. Thus, "admin@" is often already spoken for.