Once in awhile I hear from someone who is having problems with customers receiving their emails. Usually it's just a configuration problem and easily fixed. But sometimes it seems like once in awhile an email gets lost for no apparent reason. This is typically not a CFWebstore problem, but rather a ColdFusion issue.
If you send yourself an email from your site (or any function on the same server that uses a cfmail tag) you can take a look at the headers and see what the Message-ID is coming through as. If you see something like "xxx.xxx.JavaMail.SYSTEM@serverName" instead of "xxx.xxx.JavaMail.SYSTEM@serverName.domainname.com" then there's a good chance that your emails may be getting blocked or lost as possible spam. What you want is to correct the Message-ID so it has a proper mail server domain on it.
CFWebstore attempts to do this by setting the Message-ID with a cfmailparam tag. Unfortunately, some versions of ColdFusion ignore this and override the setting. So you may have to take further action, or ask your host to look into it, if you are on shared hosting. One option is to upgrade to CF8, which now always uses the mail server as set in the CF Admin for the Message-ID. If you are on an older version, your best option is to update the JVM arguments in ColdFusion, and include the mail domain there. Here's a link to a post on the Adobe Forums which outlines how to do this:
After making the change and restarting ColdFusion, send yourself another test email and now your Message-ID should be properly formatted.