Make up an e-mail address ...

No signup required - write anything to check the inbox for that email address. (Don't use special characters.)

... or choose this one

We just created this random email address - use it and abuse it!

Keep this in mind when using Flashbox

Flashbox is perfect to use when a website or app demands that you register with an email address.

You can't send emails with Flashbox, only receive. You can't receive attachments.
The address you create is not personal and has no password. Anyone who enters for example "anna" will be able to check the inbox for "anna". Choose a complicated address (like "anna777888") to minimize the risk of someone else choosing the same address.
Each email address automatically gets a unique alias address. Emails sent to the alias will show up in the inbox for the main address. People you have shared your alias address with don't know which main address it is connected to.

Flashbox is open source

Flashbox is run by the Swedish 5th of July Foundation and is based on Maildrop.