A tag added after a plus sign in an address isn't a trick or a loophole — it's a standard mail-server feature: a message sent to a plus-tagged address lands in the same mailbox as one without it. Below: what it's for, where it helps, and why it won't multiply an address. Background on email-OTP as a whole and how a one-off code by email works is covered in what email-OTP is and how to get a code by email.
What the plus-tag is and what it was built for
The syntax is simple: a plus sign and arbitrary text go between the mailbox name and the "at" sign, and the site sends mail to that full string. The receiving server does something different: it strips everything from the plus sign to the "at" sign and delivers the message to the base mailbox. The feature exists for two things: marking the source of incoming mail, and sorting — a filter rule routes mail by tag into separate folders.
Where the tag is genuinely useful
The first use is spotting who passed your address to a third party: give each site a unique tag, and if spam later arrives on that variant, the source is known — that site shared the address or failed to secure its database. The second is sorting without elaborate setup: a filter rule keyed on the tag routes mail into folders before the main inbox. Both work purely on the receiving side.
Why it stops working as a way to multiply an address
A plus-tag is not a way to create a second account somewhere that allows only one per address. Many services normalize the address at signup — the part after the plus sign gets dropped before the uniqueness check runs, so two different tags look identical, and the second signup is rejected as a duplicate. Some sites reject the plus character at form validation, before any mail is sent. Neither is an accident: services that care about the one-account rule tend to close this widely known loophole on purpose.
The risk that doesn't show up until something breaks
Even where a tag works fine for years, it carries a structural limit that only surfaces at the worst moment. Every tagged variant is the same mailbox, same password, same provider. Lose access — a forgotten password, a compromised account, a provider-side ban — and every account that ever used any tag goes down with it, all at once. There's no isolation between them; they're not separate mailboxes, just one mailbox wearing different labels. For newsletters that's irrelevant; for anything that needs to survive a failure on its own, it isn't.
When a genuinely separate address beats a tag
A plus-tag solves labeling inside one mailbox, not isolation. A separate address is the right call where a site rejects or normalizes the tag, where circuits need to be kept physically apart — so losing one account doesn't touch the others — or where mailbox access must be handed to someone else without opening your whole personal inbox and its history. The platform issues ready-made addresses from its own domain pool rather than tags or aliases on your personal mailbox — no custom domain, no custom aliases, only separate addresses per task. A one-off signup needing a single code fits a single email activation: a 20-minute wait window, refunded in full on timeout. An account you'll return to needs a mailbox rental instead: 12 hours to 60 days, extendable, but it only accepts mail from the sites listed at order time — plan that sender list up front. The trade-off between a one-off address and a rental is covered in temporary email versus a rented mailbox, and activation mechanics in disposable email for signup: how it works.
Frequently Asked Questions
Can a plus-tag be used to register a second account where only one per address is allowed?
Don't count on it: services that care about the rule normalize the address and strip the tag during the uniqueness check, so the second signup is rejected as a duplicate. A genuinely separate account needs a genuinely separate address, not a tag on the same mailbox.
Why did a site accept an address with a tag at signup, but mail stopped arriving afterward?
Accepting the format on the form and delivering later mail are different checks. The form may not have validated strictly, while a provider-side spam filter can start reacting differently to a non-standard address once signup is done. It's about how the site and provider handle the address at different stages, not the plus sign itself.
What happens to every account if the password to a mailbox with several tags is lost?
All of them are affected at once: different tags on the same address are still the same mailbox, and access is either there or not, for everything. Recovering the password restores access to every account together, but until then none can be confirmed by mail. A separate mailbox removes this risk for circuits that shouldn't depend on each other.
Order a one-off email activation for a single signup, or rent a separate mailbox with the sender list you need, in the email-OTP section.