Am wanting to migrate slowly.. by domain from 15x to 17x, (We have two licenses)
Right now we have this configuration
Inbound mail servers -->SM15.x --> and to SM17.x for other domains....
So was thinking that we could move one domain at time from SM17x.
How I was planning to do that was...
a.) set up domain on Sm17
--> make sure DKIM matches
--> (no need to change SPF because outbound email servers
-which are different - doesn't change)
b.) Copy over the directories of said "domain" .. to SM17x.
c.) change Sm15x "domain" to external - using Host adderess
d.) Run file-sync one more time between two domain directories
External (we have our 4 sets of DNS)
1.) Day before - change TTL to 1 hr for "domain"
2.) After step c.) change the the domain/sub-domain, that the users
use = to access SMTP/POP to new server IP
3.) Change auto-discovery.
not to keen to do big-bang.. but maybe the above solution is too risky too???
Opinions , thoughts, recommendations???