GMX SMS VERIFICATION Receive the GMX code on a rented number.

GMX is one of Germany's largest email providers, with sites for Germany, Austria and Switzerland and an international version at gmx.com. Registering a free mailbox asks for a mobile number and sends a code to it before the address is created. GMX then keeps the number as a way to reset the password. People rent a number for a second address kept for newsletters and shopping, a mailbox for a small business, or a test account.

GMX belongs to United Internet, the same group that runs WEB.DE, and both use a similar signup check. A German number from a real mobile range is what GMX's German signup expects, and an Austrian or Swiss number fits those sites. The free mailbox shows ads, and the signup page offers paid plans next to it.

The number at signup and afterwards

GMX asks for the number during registration and sends a code before it creates the mailbox. After that, the number appears under Security in the account settings as a password-reset route. GMX also lets you add a contact email for the same purpose. If the code is slow, GMX offers to send it again.

Add that contact email the same day, pointing at an address you control. Then switch on two-factor authentication with an authenticator app, which GMX supports. The mailbox no longer depends on the rented number, and you can remove the phone from the recovery options. GMX also sends a notice to the contact email when someone signs in from a new device.

Keeping a free mailbox open

GMX closes free accounts that go unused for several months, and it warns by email before doing so. If you want to keep the address, log in every so often. A mailbox used only as a login for other services is the kind that quietly lapses.

Because an email address is often the recovery route for other accounts, a lost GMX mailbox can take those accounts with it. Treat it as a real account, with recovery set up, even if it started as a second address. Set up recovery on day one, while the rented number can still receive a code.

What GMX allows

Several mailboxes for one person, such as a private address, a shopping address and a business one, are common and allowed. GMX's terms forbid using free mailboxes to send spam and forbid creating accounts in bulk, and GMX blocks addresses that do either. Paid plans such as GMX ProMail add storage and remove the ads, and they use the same sign-in and recovery settings.

Prices differ by country and change with stock. Check the pricing page before picking between a German, Austrian or Swiss number.