I find myself recurrently stopped while writing e-mails for a main purpose (e.g, answering a direct question from a previous mail somebody sent me) and wanting to add a second theme "taking advantage that I'm already writing you".
I don't want to be rude, in my native language this wouldn't be offensive if one writes something like "I take advantage that you've written me", but "taking advantage" seems awkward in english.
Both links below show some advices but not exactly in the context I'm looking for.
A workaround I'm using is include a separate paragraph with some connector or another phrase (e.g, "I was about to get in touch with you because...") but I would like to understand if this is the only way (the other way is more natural for me).
Another example came to my mind. It could happen during a class where a student asks about theme A and the teacher "takes advantage of the question" for clarifying A,B,C or whatever.