On cPanel server: You may access webmail, by going to http://yourdomain.tld:2095 after your domain has propagated.
On Plesk server: You may access webmail, by going to http://webmail.yourdomain.tld after your domain has propagated.
Note: Please replace "your domain.tld" with that of your actual domain name.
The hostname of your server should be in your setup email.