First of all, thank you for posting this! You'll see why in a minute.
Despite some peoples continual problems getting through to us by e-mail, I can assure you this is not the common denominator here. A much larger effort is made to answer all e-mails than one would know from reading this forum.
If you don't get a reply in 3 or 4 days then most likely it was nabbed by one of our spam filters. We get so many e-mails (having been online since 1996) that our spam defenses have to start at the server level and then finish on each computer.
Here is our spam filter:

That's the spam I pay big money each month not to see. Then for each mail box we have our own spam filter. Mine currently contains 872. I check it any time someone says I didn't respond to an e-mail and on occasion I find that was the cause. Most of the time however, I think it gets blocked at the server level, and I don't have time to scan 5700 e-mails every week to see who's in there.
My routine is simple. I check my e-mail every time I sit down in front of my computer. I read everything as it comes in. This happens on average 12 times a day and 4 or 5 times on weekends.
If the e-mail is short, and I can answer it without research, I just answer it when I read it. Otherwise I flag it so I can come back to it. I try desperately to answer all flagged e-mails within 3 days.
Here is my inbox. There is presently some 5000 e-mails in there. In addition I have 41 folders containing subject specific e-mail going back for the last 5 years. There are probably tens of thousands of e-mails there.

Here is my sent folder full of e-mails that I have sent as replies to e-mail I have gotten:

Answering an e-mail is not like checking multiple choice answers on a test. More like essay questions. No, exactly like essay questions.
The over 7000 e-mails I have personally answered do not include the rest of my entire staff. Sarah and DeVon can boast twice these numbers.
Besides everything we have to do, I think this shows real effort. I could hire people to waste your time answering e-mails with things like: Let me check with Steve and get back to you... but it would truly be a waste of time.
BOTTOM LINE: If you don't get a reply and don't want to call (I myself am like that when it comes to calling other companies) then just re-send it once or twice. If that doesn't do it, try sending with a different e-mail address. If that doesn't work, then you have my apologies and I can recommend the fine people in this forum as being able to answer a large amount of questions. I check this forum as time allows, sometimes daily, sometimes weekly.
Thanks!
Steve