To me - if you're pair programming - then you don't open your email, or you decide you're cool with the other person looking at it.
I've worked with a person who looks away, and expects you not to look when they look at their email. I'm not familiar with this "code of practice".
My question is: What's the etiquette on looking at the other person's email when pair programming?
Communication is key. You have to ask the person if:
Spending time reading e-mails is OK. The person may not be happy to remain idle for a few minutes waiting for you to read your e-mails. I worked with persons who were against doing anything disturbing during the pair programming session, such as reading/sending text messages or answering phone calls. This is a good approach when working on critical parts of the code base which require strong focus.
Although this is not what your question is about, I still think this is an important point to highlight, maybe more important than reading your colleague's e-mails, especially since some people won't dare telling you that they are unhappy waiting for you to read your e-mails (and asking themselves whether they can read them too).
Reading your colleague's e-mails is OK. Some people don't care. They leave their session opened when leaving for a 10-minutes break with their Skype and e-mail client turned on. They wouldn't care less if you will watch their browser history or their e-mails. Other people will lock their machine every time they are not in front of it and won't appreciate if you start reading their e-mails or explore the files on their machine.
Finally, the nature of the e-mails is important too:
While the person is not expected to receive personal e-mails at work, some people still do it and you probably shouldn't read them.
Some company e-mails may be confidential (and in the worst case, you won't know it until you read the message).
If unsure (and you can't discuss the subject with your colleague), just look somewhere else when your colleague is reading his e-mails, or ask to do it outside pair programming sessions.
Also, reading e-mails on a mobile device can be an easy solution to the problem. The pair programming session is not interrupted and the confidentiality is preserved.
There is no general rule: you have to discuss it with your pair.
Pair-programming is a pretty invasive practice. You do not decide to invite a colleague into your private space to discuss something. Instead, you are supposed to give up your private space and share your desktop, screen, thoughts, on a regular basis: you work very close to each other. You set up rules along the way by telling your pair what he / she can do and what not. For each pair it is different. Some pairs work well together from day 1, some pairs take weeks or months to find common rules, some never do.
The specific case of email really depends on your pair: some just don't care, some expect you to look away, some will read email during a break so you don't have a chance to see it, and so on.
