Multiple `(으)시` in a sentence for honoring target?

Question

I find that I am anxious about making sure to honor the person that I'm speaking about, especially if they are the person I am speaking to or are of a high position.

Take this interrogative sentence spoken to someone revered:

Are you, teacher, the one who sent it?

이것을 보낸 분 입니까?

I have purposefully left out the honorific final ending to the two verbs (one functioning as an adjective, of course).

Here are the options for including (으)시:

이것을 보낸 분 이십니까?

이것을 보내신 분 이십니까?

I usually end up over conjugating and using the latter...I would be grateful for some guidance, not just on what people tend to do, but what is the most honorific and/or what is beyond honorific headed into nonsensical.

update

In general I find that as my mind is constructing a sentence that does not require honoring someone, I can speak rather fluently. When it comes to the final verb conjugation, that too, I do well.

The verb-conjugation-adjectives (if I may coin a dumb phrase) trip me up; because, I have to literally pause and get a picture in my mind of the direction of each adjective phrase to figure out to whom it applies and calculate whether or not to add honor to them.

I typically am speaking Korean at church where business-speak is probably in play a good bit, but that is not the air with wich I wish to speak.

Answer 1

I've been told that essentially the more (으)시's you put in, the more polite you're being. As with English, if you go super-polite, you might be in danger of over-egging the pudding, or sounding insincere - but it will still make sense.

One '(으)시' is enough to show politeness:

선생님이 보내신 분 입니까?

선생님이 보낸 분 이십니까?

If you wanted to level up the politeness, the next step would be to make sure you use the honorific subject particle:

선생님께서 보내신 분 입니까?

선생님께서 보낸 분 이십니까?

The ultimate in politeness would be

선생님께서 보내신 분 이십니까?

That might be appropriate if a parent was asking the teacher the question in front of her child, for example, 'demonstrating' politeness. It might be a bit much if said by a colleague of the teacher with only themselves and the teacher present.

As a more general point, you don't need to worry too much about getting the politeness level every sentence exactly right - often the speech level can even vary a bit over the course of a dialogue. From what I've noticed, the most important thing to get right is the honorific forms of verbs (드시다 instead of 먹다, 주무시다 instead of 자다, etc.) Though I make mistakes all the time, the only time a Korean has actually corrected my politeness level was when I offered someone some food and invited them to "먹으세요"!