To be honest, though, I actually have two sets of responses. I have my email client set up so that I can send a response with 3 clicks. This is the reply the letters that look like mass mailings get. One form letter deserves another, I suppose. Things that trigger this response are:
- "Dear Sir" (really, there is a photo of me on the dept website, and my name is pretty much only used by women in English)
- research interests in a completely different field or sub-field
- different fonts/colors/sizes between my name and the rest of the letter
- huge list of recipients on the email (hello bcc!)
- nothing about me or ProdigalU in the letter body
The other sort of response is a non-canned personal response. I send these to people who look like they are legitimately interested in my research/my group, and I keep these emails in a folder in case my situation changes (read: I get a currently pending grant funded), and I need to find a postdoc relatively quickly. Sometimes I have had nice conversations via email with these jobseekers, and sometimes I have been able to steer them in the direction of someone who is actually looking for a postdoc. It is definitely easier to network your way into a position, since if you come recommended by someone known to the PI, it is better, but I know many people who have cold emailed their way into a postdoc.
So I guess when it comes down to it, if you are looking for a postdoc and want to be taken seriously, Google is your friend. You should be able to use the correct gender when referring to me (or stick to the gender neutral Dr. or Prof. as an address). You should articulate quickly and clearly WHY you are interested in a postdoc with me. Even better if you can articulate HOW you think you will benefit from and/or provide benefit to my group. If you are coming from a different sub-field, you should acknowledge this and explain why you want experience in mine. Your letter should be clear and concise--it is by far the most important thing when cold emailing for a postdoc. More important than your CV, which I won't even open if my interest is not caught by your email. I like helping people out, and dispensing advice (hence the blog), but it is only worth it if I think the request is legit.