I am working as a researcher in a research lab, and I want to apply for a Ph.D. position. I have read that most of the professors read emails sent through professional email-id only. But my current professional email id is restricted to be used in the research lab only. What should I do to make my application email stand out?
Use an email which sounds serious, like [email protected]. Also have your full and real name as a name in the From: field. Whether it is a professional email does not matter. But it should look professional, in the sense mentioned.
Keep your email itself concise. Make it clear why you want to apply to this specific place. This, of course, means that you apply to a few selected places which you picked for the specific research they are doing. Note that just looking up the professor's most recent papers and saying "I find $PAPERTITLE1 and $PAPERTITLE2 very interesting." is likely not going to work, for several reasons.
Attach a CV, and possibly some other documentation. Don't say "I can send you a CV upon request." You want to minimize the professor's work to learn about you. If possible, also mention who they could ask about you, either in the CV or the email itself.
Don't misspell the addressee's name, or their institutions name, etc.. And address them directly. Emails starting with "Dear Sir" look like you sent them to many people.
An institutional email address is not a requisite nor it does make your inquiry looks less serious.
I personally was suggesting a receipt request, but apparently most people dislike the option no matter the purpose. I personally can see the difference between a peer of mine pushing for some action and a student in trepidation. However, as the chance that I would be the recipient is ridiculously low, don't ask for a receipt.
Be cautios and clear filling the subject field. I do suggest something like "PhD openings inquiry, name surname" or so.
I also suggest that the body part shows that you didn't choose the particular recipient at random. This can be very short, at this stage.