It's not uncommon for employers to contact potential interviewees by email, rather than letter or telephone. Doing so offers several advantages for the employer -- email is fast and cost effective relative to snail mail. It's also likely to elicit a quick response from the applicant. For the potential employee, it is an opportunity to impress the interviewer prior to the appointment.
Email and attachments
The email inviting you to interview will probably be very brief. It will offer you a date and time to attend. There may be file attachments with information about the job, the company and their recruitment procedures. Read these carefully and save any documents to your computer for future reference. It may be a good idea to have any relevant documents open while you compose your response.
Make sure you don't need to contact someone with a different email address to the sender. If this is the case, it will be specified in the body of the email. Use the “Forward” facility rather than “Reply,” in order to keep the original email intact. Insert the email address into the address bar of the email. Otherwise click “Reply.”
You can leave the subject line as it is, unless you've been given a reference number which doesn't appear in the subject line of the original email. It makes sense to add this in, so the employer can access your mail quickly. This also demonstrates that you're efficient and considerate.
Leave a blank line under the salutation and add a heading, such as “Vacancy for pastry chef -- (reference number if you have one).” Leave another blank line. Thank the person you are writing to for the opportunity to attend the interview. State whether the date and time are acceptable to you. Suggest alternatives if it's not. Respond to any further questions and end the email with “I look forward to meeting you.” Sign off with “Yours sincerely,” if responding to someone by name, or “Yours faithfully,” in the unlikely case that you haven't been given a name. Put your full name at the bottom of the email. You can add your title in parentheses if you wish.
Dos and don'ts
Always use correct spelling and grammar. Don't use all capital letters. Never use abbreviations or “text-speak.” Always research the company carefully. Don't ramble; be concise and clear. Double check all the details, and that you have followed any instructions given, before pressing “Send.”