name of domain AD Different than messaging domain name

Hi,

my problem is : when the user create ticket in spicework portal and the helpdesk accept this ticket , the user don't receve the mail automatic. I think that the cause of problem is ;

the domain name of AD is : dz.mea.lafargeone.net

but  the domain of messaging is : scmidz.com

how can i fixed in spiceworks that the domain of messaging is : scmidz.com and not
dz.mea.lafargeone.net .

thanks in advance