Plus addressing and automatic folders

Every Mailocity address accepts a tag after a plus sign. Mail sent to alice+news@example.com reaches alice@example.com, so Alice can hand out a different address to each shop or newsletter without creating aliases.

Aliases take tags too, whether a team alias (sales+orders@example.com) or one a user took on a shared domain (ali+shop@freemail.example): the mail reaches the alias's account, is filed by tag when plus folders are on, and is refused when the user refuses tagged mail. People can send from an alias with a tag as well.

Folders for every account

Each new account starts with six folders: Inbox, Drafts, Sent, Archive, Junk and Trash. These folders carry their roles for mail apps and cannot be deleted. People can create as many other folders as they like.

Filing tagged mail in its own folder

A domain administrator can turn on plus-address folders for a domain. With it on, mail to alice+news@example.com is filed in a folder called news instead of the inbox. If Alice has no such folder yet, Zappocity creates it when the first message arrives.

An existing folder with the same name in any case is reused, so mail to alice+projects@ lands in a folder Alice already called Projects.
Tags may use letters, digits, ., _ and -, start with a letter or digit, and be up to 64 characters. Other tagged mail goes to the inbox.
Tags that name Drafts, Sent, Junk or Trash go to the inbox, so nobody can drop mail into those folders from outside. +archive files into Archive.
An account with 200 or more folders gets no new folders; further tagged mail goes to the inbox.
If a message is sent to both alice@ and alice+news@, Alice gets one copy, filed by whichever address came first.

The setting is off by default, because with it on anyone who can email an account can create folders in it.

Turning it on

In the tenant manager at /manage (see Team administration), the Domains page has a Plus addressing card: By domain has a switch for each of the tenant's domains (File in a folder named after the tag, for people with the Domains part), and By mailbox has each mailbox's own choice (for people with the Mailboxes part; Show every mailbox lists those that follow their domain too). The same switch is in each domain's Mail settings. Through the API:

PATCH /v1/tenants/{tenantId}/domains/example.com
Content-Type: application/json

{"plusFolders": true}

GET /v1/tenants/{tenantId}/domains/example.com shows the current value. Folders also need the Plus-address folders feature in the plan.

Each user's own choice

Every user can override the domain under Settings → Plus addresses in webmail, and an administrator can do it for them (the Plus addressing card's By mailbox, or Edit on the user, Mail to name+tag@):

Choice	What happens to mail for `alice+news@`
Follow my domain's setting	Folders if the domain has them on, else the inbox. The default.
Keep it in my inbox	Always the inbox.
File it in a folder	A `news` folder, even when the domain has folders off. Needs the plan feature.
Refuse it	Turned away like mail to an address that does not exist. Mail to `alice@` still arrives.

Refusing is useful once tagged addresses start getting spam. Filters still run on everything that arrives. Through the API, the account's plusMode is folders, inbox, refuse or null; users call PUT /api/mail/plus-mode.

Tags can also be given as a subdomain: with subdomain addressing on, news@alice.example.com reaches alice+news@example.com.