Yup, that is a tough one! I have both gotten and received those emails. I think there are three details that are often omitted from such emails, decreasing the changes of a response. These are:
What do you want?
I think the biggest reason not to answer to an email for me, is that there is no clear question for me to address. Here is an example based on an email I got a while back:
I really liked your paper on <topic y> and I was wondering if we could collaborate on this?
Eagerly awaiting your reply.
This is the type of mail that might get stuck in my inbox. “I was wondering if we could collaborate on this?” might look like a clear question, but it is not. What do you mean with a collaboration? A paper together? A coffee where I give feedback on your idea? A review of a paper already written? My guess is this student does not know it either. So figure out what you want before you email.
Of course, this does depend on who you are asking! Even if I do not know you, if you are a student of a friend, or if your topic is really of interest to me, I might be up for “a chat”. If you are further away, response to such an email is less likely.
What does it mean to the reader?
A second problem with the above email is that the reader does not make it clear what the reader will get out of this interaction. That might sound really goal driven and potentially even mean, but there are just 8 hours in a workday. Faculty members have to make choices on where they spent time, so they usually only respond to interactions that sound really viable or cool. Of course, this is a personal choice, some faculty might be very inclined to take “serendipitous” meetings, but all our time is limited.
How much time do I need to spend?
The third problem with a vague email is that the reader does not know how much time will this take. Although I recently found out that many faculty member in my department do not plan their days (more on that later), they probably still have a vague idea on how much time there is in their schedule for random meetings/service. They will also know where their current priorities lie, f.e., if they are looking for a new paper on topic y or that they are moving on to other things. So give the reader enough info such that they can estimate the workload.
A good example (also based on a real email I got)
I’m in the process of re-implementing your algorithms as proposed in  and . However, are any formal definitions or algorithms of the used metrics available? While the textual description of the metrics seemed clear enough at first, during implementation I still hit upon some ambiguities.
This email has information on the above three points:
- What they want? -> information on details of my algorithm
- Why? -> So they can replicate my work
- How much time? -> Although it is not in the email, I can figure out that I can do this in a meeting of about an hour.
After this email, I scheduled a Skype meeting and talked the student through our definitions. Because it was clear what I should do!
Bonus: The subject line
Related to these points is, of course, the subject line. Try to get at least one of the above three points into it. Make it clear in the topic what you want, why and how long. So, do not use “contact request” or something like this, but say “A coffee to talk about topic y”.
Bonustip: if you have met the reader in person, refer to that, so they are more inclined to help out. Of course I still remember meeting Bertrand Meyer, but I had to introduce myself three times before he did 😉
Finally, sometimes they still won’t get back to you. That is okay, no one in fact owes you an answer. Try to think of solutions or other plans in that case, preferably soon, not after you did not get a response.
This post has a few really good tips along the same lines!