It depends on the amount of emails the person you are writing to gets. If you write to a high status person who gets 100 emails per day, being concise is important. There are a lot of people who think they spend too much time with email and who want to spend less time on email.
Let's say I was a meetup and had an interesting discussion with someone. In it he referred to a scientific paper but when you come home you have forgotten the specific paper.
You could write the person: "Sorry to bother you but could you please tell me the name of the paper you spoke about yesterday? Of course only if you don't have to do this, if you don't find easily."
You could also write: "I really enjoyed our conversation about topic X yesterday. You referred to a paper about topic X, making point Y? Can you send me the link?"
The second version is more likely to received positively. The fact that you tell me you enjoyed the conversation with me is information. It's friendly. Telling me specifically what paper you want helps me. It makes it easier for me to help you because I don't have to go back and reply the conversation in my mind to find with paper you could mean.
As a general rule, say sorry when you make mistake. Apologize for your mistakes. Don't say sorry when you aren't making mistakes.
If you want to be nice and friendly, give the other person a compliment. Given out compliments implies that you have a status that's high enough that the other person cares about your opinion. It also validates the other person.
Getting a compliment puts me in a positive mood. Reading "sorry to bother you" rather puts me in a negative mood.
As a general rule, say sorry when you make mistake. Apologize for your mistakes. Don't say sorry when you aren't making mistakes.
I figured this out at some point, but I really wish I had figured it out fifteen years earlier.
I would add an exception to the rule: I recall someone around here (I think quoting HPMoR) distinguishing between apology as regret and apology as submission. Some people only hear the latter. The rule does not work with them. They can usually be identified by explicitly demanding apologies or at least angling for them. Someone you have actually wronged probably doesn't want an apology; they either want you to go away, or they want you to suffer.
Do the following things in email tone lower status?: