tl;dr Scroll to the bottom for instructions on using a Google Script you can use in Google Docs spreadsheets to extract your email@example.com email addresses you’ll need to migrate before Otherinbox officially sunsets “Defender”.
Otherinbox first launched as a service that let you choose a username which was prepended to a subdomain that you could use to form email addresses on-the-fly. My subdomain was bryan.oib.com (‘oib’ was the shortened domain for “Otherinbox”), so when required to supply an email at checkout at an online store, I would give “firstname.lastname@example.org”. This was endlessly entertaining to do in-person; salespeople would hear their company’s name in my email address and say, “no, we need your email.” I got quite good at pitching the concept. Often the salesperson would relent and accept the funky email and say, “huh, that’s really cool.”