Before you start, to use IMAP, you will need to ensure that IMAP has been enabled in the Google Apps settings. 


Mail Settings => Forwarding and POP/IMAP => IMAP Access: => Enable IMAP


Google Apps POP settings will override your e-mail client/app settings for leaving/not-leave messages on the server. To set it in Google Apps;


Options => Forwarding and POP/IMAP => Number 2 selection pull-down


POP Settings:

Server: pop.gmail.com

Port: 995

SSL: Yes, you must use SSL (Google Apps policy)

Username: Your full e-mail address (include your login name and the @yourcompany.com)

Password: Your normal e-mail password (assuming you reset it and it has already synced, as above)


IMAP Settings:

Server: imap.gmail.com

Port: 993

SSL: Yes, you must use SSL (Google Apps policy)

Username: Your full e-mail address (include your login name and the @yourcompany.com)

Password: Your normal e-mail password (assuming you reset it and it has already synced, as above)


SMTP Settings: (Regardless of whether using POP or IMAP)

Server: smtp.gmail.com

Port: 587

TLS or StartTLS: Yes, use TLS, you must use TLS (Google Apps policy)

SMTPAuth: Yes, you must authenticate to (SMTP) relay through Google Apps, see below

Username: Your full e-mail address (include your login name and the @yourcompany.com)

Password: Your normal e-mail password

NOTE for SMTPAuth: For some e-mail clients/apps, there is a simple checkbox that allows using the “same settings as my incoming server"