if we want to use pop\imap, can I use mail.contoso.com or do I need to use pop.contoso.com and imap.contoso.com

You can use anything you like. The name being used doesn't matter. All you need to ensure is that whatever name you are telling the clients to use matches one of the names in the SSL certificate - preferably the common name for maximum compatibility. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources | In the UK? Hire Me.

Thanks. I read on technet - http://technet.microsoft.com/en-us/library/dd351057.aspx Enter the FQDN of your Hub Transport server if you'll be using mutual TLS to help secure Internet mail or if you'll be using a Hub Transport server for POP and IMAP client submission. if you'll be using a Hub Transport server for POP and IMAP client submission. is this server.company.com? if you have multiple then enter all of those or will mail.contoso.com work as well?

The FQDN can be anything you like. If you are using mail.example.com for your external host name, then use that for everything - OWA, ActiveSync, POP3, IMAP, Outlook Anywhere. Keep it simple, and it also keeps down the number of names that you require in the SSL certificate. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources | In the UK? Hire Me.