"Would it be" vs "Will it be"

I was writing an email to my colleague and as part of it I wrote

Would it be possible for you to help me with this?

I felt a bit awkward after sending the mail. Should it be would or will? I know that would is a past form of will but it is also used to indicate politeness. In this case, it was extremely important for me to sound polite and formal. Please advise regarding the correct usage.

I have already seen these questions: "Would" vs "Will" and "Would" vs "Will", but I need some more insights as to when would is used as part of a question asking for a favour.

Since "would" is subjunctive (http://www.learnersdictionary.com/search/subjunctive[2]), it does sound more polite, while "will" comes off as a bit more directly.

If I understand your situation correctly, "would it be possible for you to help me with this?" connotes, "would you be willing to help me with this, provided you had the knowledge and/or resources?"

On the other hand, "will it be possible for you to help me with this?" says, "will you or will you not help me?"

So, depending on the nature of the question and your knowledge of your colleague's skills, schedule, and other necessary resources, either could apply. You are correct in feeling that "would" is more polite. When used correctly, the subjunctive mood is more polite and often more acceptable.