People get sick. Their cars break down. Loved ones are rushed to the hospital. Whatever the reason, college students will likely have to be absent from class every now and then. Using e-mail to get in touch with a professor whose class you were absent from is not only proper etiquette, but it might be one of the only chances you get to find out what you missed and if and how you can catch up.
Note your class and section number in your e-mail's subject line. You may also want to add a keyword or phrase like "absence" or "attendance issue."
Write to the professor before the absence will take place, if at all possible. For example, if you need to miss class due to a conference or trip, let your professor know before. That way you can be brought up to speed before your absence occurs, which means less runaround for both you and your instructor on your return. Otherwise, draft and send your e-mail as soon as you can get to a computer, even if an unexpected absence has already occurred. For your professor's records, always note the date of your absence.
Address your professor formally. You may use the "Dear" salutation, or simply type out the professor's first name and title (e.g. Dr.) followed by a colon.
State the purpose of your e-mail up front in clear, plain language. Professors are busy people and often receive dozens of e-mails a day. Don't make your professor have to comb through your e-mail looking for your objective. Your first sentence should note that you were, or will be absent, and that you want to make sure you are on track with the rest of the class when you return.
Check your syllabus. Never ask a professor: "What did I miss?" before checking the class schedule on your syllabus to see if the answer is there. You can also ask a classmate. Don't press your professor to give you information you could easily gather on your own. Instead, keep questions as specific as possible and only ask those questions if you really need an answer immediately.
Keep your e-mail short and to-the-point. Again, professors don't want to spend a great deal of time deciphering the purpose of any given e-mail. Be professional. Ask yourself what the professor really cares about. Do you think she will be worried about your absence? Address those worries. If you don't think your professor really has the time or inclination to care, don't spend time apologising or making excuses. Sometimes, writing an e-mail regarding an absence is nothing more than a courtesy and should contain only a brief statement noting the fact that you were/will be absent and your intention to not fall behind.
Offer only appropriate information. You need not expand on your excuse and may choose not to go into detail about your reasons unless you feel you will have attendance problems in the future.
Be polite. Again, you need not apologise profusely for having missed class, but be aware that professors work hard to provide a successful learning experience. Let them know you appreciate their work, even in absentia.
Proofread your e-mail before sending it and make appropriate changes. Remember you want to come across as a professional.
End your e-mail with a formal closing like "Sincerely," and then type out your full name. Underneath your name you might also want to reiterate what class and section number you are enrolled in.
If available, always read your professor's e-mail etiquette policy contained in her syllabus before sending her a note. Sometimes professors have certain rules regarding content and address and these should be observed closely in order to communicate your attention to detail and concern for your teacher's time and efforts.