do i use [email protected] as my username
Sim.
school.edu as my server or gmail.com as my server,
O domínio permanece gmail.com, não seu domínio.
Como o artigo de suporte menciona:
Configuring IMAP access for your Google Apps email address is very similar to configuring it in Gmail. However, any time you're asked for your username during the configuration process, you'll need to enter your full email address, including your domain (username@your_domain.com). All other settings are the same.