The reason why I started investigating the chart further than "will there be a relationship" is that I saw many horary astrologers finding much stuff in one only chart. Most say we should be able to see beyond the original question in the first chart cast, so I tried to dig deeper without casting separate charts for each detail.
This is one of those hard to pin down issues in horary. On the one hand you have Astrologers such as John Frawley, who counsel that the Astrologer should address themselves to the question asked and not volunteer any other information. On the other there are Astrologers who love giving lots of descriptive detail. my own view, for what it's worth can be summed up as 'Frawley But....' That is I am to keep things as short as possible (allowing for the explanation of how I've come to judgement) but including material that is clearly pertinent to whether the matter will or will not come to effect. For some questions, there are clearly more than one two significators and houses, indeed with questions related to house purchases there may be four or more significators involved - buyer, seller, property, and one or more estate agent.
That's one of the reasons it's important to discuss the question with your sitter/client, as there may well be pertinent side issues involved, and you're right, having to cast more than one chart is time consuming and detracts from the elegance of Horary. But make sure that the issues are pertinent before you provide additional information. If you think the question chosen isn't exactly what the sitter really wants to ask, then talk around the question to see if there are other issues that should be read for.
As it's your own question, then you probably did intend to consider the issue of communication, and that's fine. If I had been reading for your question I wouldn't have read for it, on that question but if you'd stressed the issue more in the background I might well have picked it up and included it in my reading. In which case the letter would be Jupiter, and as the Moon is applying to Jupiter, I would conclude that he would receive it. Whether he would reply is a bit more difficult, as there is no 'reply' letter in existence at that point (if they were it would indeed be Mercury). I might look to see if the Moon is in any dignity of Jupiter (meaning that he would be positively disposed to it) and even if Jupiter is in any dignity of the Moon - mutual reception would indicate a strong probability that he'd reply and then we can go on and look at Mercury.
I also wanted to share something: my Bday is next month and today I cast a chart asking if there will be any communication between me and this man around my Bday, will he congratulate or at least respond to my previous letter. And guess what - the chart is almost the same! Same significators, just the Asc is in the middle of capricorn already. If you want to take a look, I'll appreciate it: September 26, 3:47 pm, Sofia, Bulgaria. The Moon again translates light between Mars and Venus, our 3rd house rulers. But here she first opposes Venus (his 3rd house ruler) then squares Mars (my 3rd house ruler) and she is only 2 degrees from this happening. As far as I remember Lillie says the type of aspect doesn't matter but is that so?
Is there translation of light signifying possible communication in both charts or am I off?
OK, I also find in both charts aspect between our 5th house rulers. In the one you took a look at, it's upcoming square between Venus and Mars, not the best possible but still existing. In the one I cast today, it's between Mercury and Jupiter, it's a trine and it's very close... Should I consider these too? As possibility of a meeting or flirt or communication?
Again the focus of your question as stated is on communication....more specifically will he communicate with you. The Moon is again in Aquarius (we're a lunar month on) so He's still ruled by Saturn (and so is predisposed to a relationship). His third, is the radical ninth - cusp in Libra and is ruled by Venus. Venus is currently in the seventh House (with him) but the Moon is applying to an opposition with Venus, so I take that as being the point at which he will or will not send the communcation. Saturn is in the sign of Venus (you want the communication) but Venus is in the Detriment of Saturn (so I'm not sure he will send it or it will not be a positive response). Venus is applying to a sextile with Saturn, though it's currently in a partile square with Mars, (your third house ruler and therefore your communication to him).
At the same time Mars is being squared by the Moon. So he got your letter (confirming the first chart), and he will shortly make a decision to respond to it. If he does you will certainly receive it. The issue is whether it will be positive news or not what you had hoped.
For positive news, there is the Moon in the dignities of Saturn, Venus in the dignity of Mars (your letter) a forming sextile between Venus and Saturn and Mars in a dignity of Venus. However the mutual reception between Venus and Mars is very weak.
For a negative response we have Moon opposing Venus (either suggests no letter or a negative letter) Venus in the Detriment of Saturn and Venus squaring Mars and Venus squaring the North Node which it will perfect in the same degree as Saturn.
There's indicators in both directions, though I think the negative ones are rather stronger. I don't think that will necessarily be the end of the matter. It could just be that there will be difficulties which will delay the letter arriving or he is in two minds what to do. He's predisposed to a meeting but the other indicators suggest doubts.
Don't be surprised if you get something that is not positive but don't treat it as the end of the matter. Also don't be too disappointed if the communication doesn't arrive 'in the time frame'' This is not going to be too easy but again I don't seen this as a complete dead end. There's hope yet.
Lilly doesn't say squares don't matter, but he does say that something can still come to pass even if there's a square aspect involved, it just denotes difficulties or delays. However in this case we want not only the letter to arrive but also it's contents to be positive. For example the sextile between Venus and Saturn may be an easy aspect but that only suggests the letter will arrive quickly it doesn't guarantee the contents.
The aspect which worries me most here is the opposition between Moon and Venus, which suggests no response or a very delayed response, or a response that will not satisfy you.
Unless the letter says 'no chance' don't end things here, I think there is enough in the chart to keep this going a bit - he has positive feelings.