Verb tenses when asking a question

How can I establish time period when trying to ask someone about a question that was asked some time ago?

I asked you a question in my last email, but I wasn't sure (this is happening now) if it went through.

My asking took place sometime in the past, but my being not sure happened a little after my asking. So would it be more correct to say "I had asked you a question"? Just how much information is allowed to be assumed that they are happening around the same time?

I asked you a question, but you must have forgotten, since you still haven't gotten back to me.

Is it okay to use present perfect instead of simple past? I want to assume that my asking a question and her forgetting it happened around the same time, but it seems more natural to use present perfect here. Am I mistaken?

EDIT: I have additional questions:

I know this is kind of too late, but when I say "I asked you a question in my last email, but I wasn't sure (this is happening now) if you received it," don't I have to say "had received" in order to be correct? I think (write email -> try to send it -> be unsure if you received it) works here as well, but why do I have to use past perfect here?

Answer

The guiding principle should be don't use Past Perfect unless you really have to.

The uncertainty occurred after the asking - chronologically, and in the narrative sequence of OP's text. That's what normally happens when you report a series of events...

I did this. Then I did that.

It's grammatically possible, but completely pointless in most contexts, to express that as...

I had done this. Then I did that.

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In OP's second example, it's pretty much impossible to avoid Present Perfect with the word must. You could get away with ...but it must be [that] you forgot..., but it's a bit "starchy". Present Perfect is perfectly natural here.

Consider, for example,...

1: You didn't answer the doorbell when I rang, so you must have gone to work early.
2: You didn't answer the doorbell when I rang, so you must have been in the shower.

Clearly in #1, the action in the present perfect clause (you going to work) happened before the simple past (I rang). But in #2, you being in the shower happened at the same time as I rang. That's not a problem in English; if the chronological relationship between actions is obvious from context, it doesn't always have to be made explicit by the verb forms.