Gmail has an interesting characteristic that falls somewhere between “really cool feature” and “strange parsing bug”, depending on how you want to look at it. Whatever the underlying cause, the end result is that you can create custom aliases to your Gmail account that can be used to help differentiate your accounts. There are two different ways. The first one is the appended alias.
The second behavior, which I believe is unintentional, is delimiter invariance. In most e-mail systems, “FirstLast@gmail.com” and “First.Last@gmail.com” are treated as unique identifiers. They may be bound to the account on the back end. Gmail appears to use complete delimiter invariance in their systems, though. My e-mail address does not currently contain any separators, but if I sent e-mail to first.name, f.irstname, firstnam.e, or even firstname.lastname@example.org they all route to my primary e-mail account. This is especially interesting because another Internet user in another part of the country with a similar name, has registered the same e-mail address. Gmail allows periods when creating the account, but ignores them. I occasionally get e-mail directed to this other individual because of this issue.
Combining these two, you can sort and filter your e-mail a bit before it even reaches your inbox by making your address uniquely identifiable. It’s a pretty neat feature.
One issue that’s starting to crop up lately is Google’s incorrect handling of messages with delimiters in their address. It makes it possible for multiple people to have accounts with the same name, and incorrectly route e-mail between them. I use a variant of my name as my e-mail address. Several other someones, with different first names but the same last name, use the same e-mail address except with a “.” in different places. All of the messages come to me, whether they’re sent to me as email@example.com or firstname.lastname@example.org.
This isn’t an isolated problem, either; a friend of mine named Alex recently learned all of the details of someone’s European trip because they were using Alex.Name@gmail.com while said friend was using AlexName@gmail.com. I’ve learned intimate details about a Canadian’s divorce, custody battle and asset division fight, along with real estate purchases; a serviceman in Ohio signed me up for a Military.com account. No matter how many times I reply to all informing these people, it won’t stop because it’s a systemic issue.
Google really needs to fix the handling of addresses with delimiters, because this bug has severe and far-reaching privacy implications.