Moving to new server... impacts on current email account

hi there,

I have a client who uses squirrel mail which forwards to Outlook, he is with another host.

I am in the process of transferring the domain name to my account with dream host.

from the time I transfer the domain to dreamhost, if I have not created the new email account with dream host, where are the emails going?

while the domain transfer is occurring, what downtime is he looking at for his email and how do i minimize it?

any advice on this matter would be greatly appreciated I am worried sick, I do not want him to lose email capabilities he gets like a thousand everyday.

thanks so much, I wonder why live chat isnt on,