My question is, I have been sending out mail to drum up work with my business.?

OK here it goes Normally for every hundred letters I mail out United States Post office , I will get from 1 to 4 new customers, now every week I was sending out 800 mail outs and, the day homeowners get them I get a phone call from them.
this is how italways works.
now 2 weeks ago I did a mail out to one area 400 then next day 400 to another area in that same town.
thing is I had 0 response from them mail outs
this never happens not when I mail out that many
Question is How would I find out if they went to these homeowners.
oh my mailing list is good, I double check each address over the internet
I also Have caller I.D. and checked all the calls I had over the past two weeks even the hang ups none are from them two areas.
I always get responses normally a day after the mail out always within a week this is over two weeks now.
all other areas I mailed out to responded either by phone or mail

I am adding this the area I did the mail out to I checked it out real good it is a good area just like the other areas that i hit a few miles from it.
the average age is between 35 and 65 etc. I checked the areas I mail out to real good I drive in them and check out everything about them over the internet before picking were I am doing mail outs.
I been doing this for a few years now and I know my areas, think some how my mail did not reach its destination for one reason or another?

random mailouts are not always a guarentee of a result regardless of how many letters you post.

it could very well be the demographics of your last few mailouts were on target for your business and the lack of reponse could show that the demos from those areas are not interested in your product or service or that there is another competitor already servicing that area.

Good marketing is more than just posting a letter, it requires an analysis of the demographic that will be most receptive to your product and then targeting them in such away as to gain interest from them.

all random letters will draw is a lucky dip of responses.

Looks like your luck just ran out here, i would suggest that you sit down and really analyse your business perhaps with someone who doesn't have an emotional attachment, consider your demographic and form a strategy on how you will gain their attention.

you may also save yourself heaps of money as well in wasted mailouts.