I am in a situation where I need to tell my current employer that I am leaving. I know what I want to say in the body of the email I am using to do so, and have that written out in full. Problem is, I am not sure of what sort of subject line would be appropriate in this situation. Something like "Letter of resignation" sounds too harsh, but I want to make it clear as well that from the outset, this is not a negotiable thing, but merely me making it clear that I am taking the steps to move on from this place of employment to my next opportunity.

What sort of subject line would be appropriate here?

I am in a situation where I need to tell my current employer that I am leaving. This will be the first my manager hears of it; for reasons I don't want to discuss here, we have not had a meeting about this. I know what I want to say in the body of the email I am using to do so, and have that written out in full. Problem is, I am not sure of what sort of subject line would be appropriate in this situation. Something like "Letter of resignation" sounds too harsh, but I want to make it clear as well that from the outset, this is not a negotiable thing, but merely me making it clear that I am taking the steps to move on from this place of employment to my next opportunity.

What sort of subject line would be appropriate here?