Original source: lifewire.com/easy-gmail-address-hacks-1616186
Gmail addresses are pretty cool, but you actually have more Gmail addresses than you think you do, even if you only have one account. Here are some easy hacks to give yourself a lot of email addresses. Don't use this to spam people or register twenty Twitter accounts. Most (but not all) major sites have already figured out these tricks. However, this works great when it comes to automatically filtering your email or figuring out where someone got your email address.
Add a period
Does your Gmail address have a period in it somewhere? Many people find that their full name is available if they space it out with a period. "My Example Name" would turn into something like email@example.com because Gmail addresses can't have spaces.
As it turns out, my.example.name@gmail is the same as firstname.lastname@example.org or email@example.com. That's because the periods don't matter to Google at all. They're just filtered out. You could just use the period when you give your email out to people (to make it easier to remember) and skip it when registering for an account.
You can sometimes use this to your advantage if you want to register for something using the same email address more than once. We've used this to register separate family accounts on websites that ask for email addresses but don't actually email anything. Some sites are savvy enough to pick up on the fact that all those email addresses are really the same address, so it's not always going to work.
Add a +
Not only can you add a dot anywhere and still get email at that address, you can also add a secret tag. You can add a plus sign and another word, such as firstname.lastname@example.org. That's still going to go to myexamplename@gmail - the same address as the previous examples. The difference is that you can now target that address for automatic filtering.
That's it. With this new-found knowledge, you could register different addresses at different sites in order to filter your results. Print business cards with tags. Give clients different tags for different projects. The sky is the limit. You could even use this trick to filter out spam: if you sign up for a contest, use a specific tag and then add a filter to send those messages straight to the trash when the contest is over.