Masked email: Fastmail's Masked Email API, MaskedEmail/get and /set (ME-1, ME-7a, ME-16)

Advertised as https://www.fastmail.com/dev/maskedemail in the session and on
every account that may hold masks. Masks created through it start pending
unless the create sets a state; pending can't be set again once left; state
and the other mutable fields map onto the same records the x: API uses.

crates/jmap-proto/src/object/fastmail_masked_email.rs

@@ -0,0 +1,190 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Coffey Labs
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+//! Fastmail's published Masked Email API, `MaskedEmail/get` and
+//! `MaskedEmail/set` under `https://www.fastmail.com/dev/maskedemail`
+//! (masked-email spec, "The two APIs"). The ids are the same as
+//! `x:MaskedEmail`'s, so an id is one mask whichever API reads it.
+
+use crate::{
+    object::{AnyId, JmapObject, JmapObjectId},
+    types::date::UTCDate,
+};
+use jmap_tools::{Element, Key, Property};
+use std::{borrow::Cow, str::FromStr};
+use types::id::Id;
+
+#[derive(Debug, Clone, Default)]
+pub struct FastmailMaskedEmail;
+
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum FastmailMaskedEmailProperty {
+    Id,
+    Email,
+    State,
+    ForDomain,
+    Description,
+    LastMessageAt,
+    CreatedAt,
+    CreatedBy,
+    Url,
+    EmailPrefix,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum FastmailMaskedEmailValue {
+    Id(Id),
+    Date(UTCDate),
+}
+
+impl Property for FastmailMaskedEmailProperty {
+    fn try_parse(_: Option<&Key<'_, Self>>, value: &str) -> Option<Self> {
+        FastmailMaskedEmailProperty::parse(value)
+    }
+
+    fn to_cow(&self) -> Cow<'static, str> {
+        match self {
+            FastmailMaskedEmailProperty::Id => "id",
+            FastmailMaskedEmailProperty::Email => "email",
+            FastmailMaskedEmailProperty::State => "state",
+            FastmailMaskedEmailProperty::ForDomain => "forDomain",
+            FastmailMaskedEmailProperty::Description => "description",
+            FastmailMaskedEmailProperty::LastMessageAt => "lastMessageAt",
+            FastmailMaskedEmailProperty::CreatedAt => "createdAt",
+            FastmailMaskedEmailProperty::CreatedBy => "createdBy",
+            FastmailMaskedEmailProperty::Url => "url",
+            FastmailMaskedEmailProperty::EmailPrefix => "emailPrefix",
+        }
+        .into()
+    }
+}
+
+impl FastmailMaskedEmailProperty {
+    fn parse(value: &str) -> Option<Self> {
+        hashify::tiny_map!(value.as_bytes(),
+            b"id" => FastmailMaskedEmailProperty::Id,
+            b"email" => FastmailMaskedEmailProperty::Email,
+            b"state" => FastmailMaskedEmailProperty::State,
+            b"forDomain" => FastmailMaskedEmailProperty::ForDomain,
+            b"description" => FastmailMaskedEmailProperty::Description,
+            b"lastMessageAt" => FastmailMaskedEmailProperty::LastMessageAt,
+            b"createdAt" => FastmailMaskedEmailProperty::CreatedAt,
+            b"createdBy" => FastmailMaskedEmailProperty::CreatedBy,
+            b"url" => FastmailMaskedEmailProperty::Url,
+            b"emailPrefix" => FastmailMaskedEmailProperty::EmailPrefix,
+        )
+    }
+}
+
+impl FromStr for FastmailMaskedEmailProperty {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        FastmailMaskedEmailProperty::parse(s).ok_or(())
+    }
+}
+
+impl Element for FastmailMaskedEmailValue {
+    type Property = FastmailMaskedEmailProperty;
+
+    fn try_parse<P>(key: &Key<'_, Self::Property>, value: &str) -> Option<Self> {
+        match key {
+            Key::Property(FastmailMaskedEmailProperty::Id) => {
+                Id::from_str(value).ok().map(FastmailMaskedEmailValue::Id)
+            }
+            Key::Property(
+                FastmailMaskedEmailProperty::CreatedAt | FastmailMaskedEmailProperty::LastMessageAt,
+            ) => UTCDate::from_str(value)
+                .ok()
+                .map(FastmailMaskedEmailValue::Date),
+            _ => None,
+        }
+    }
+
+    fn to_cow(&self) -> Cow<'static, str> {
+        match self {
+            FastmailMaskedEmailValue::Id(id) => id.to_string().into(),
+            FastmailMaskedEmailValue::Date(date) => date.to_string().into(),
+        }
+    }
+}
+
+impl JmapObject for FastmailMaskedEmail {
+    type Property = FastmailMaskedEmailProperty;
+
+    type Element = FastmailMaskedEmailValue;
+
+    type Id = Id;
+
+    type Filter = ();
+
+    type Comparator = ();
+
+    type GetArguments = ();
+
+    type SetArguments<'de> = ();
+
+    type QueryArguments = ();
+
+    type CopyArguments = ();
+
+    type ParseArguments = ();
+
+    const ID_PROPERTY: Self::Property = FastmailMaskedEmailProperty::Id;
+}
+
+impl From<Id> for FastmailMaskedEmailValue {
+    fn from(id: Id) -> Self {
+        FastmailMaskedEmailValue::Id(id)
+    }
+}
+
+impl JmapObjectId for FastmailMaskedEmailValue {
+    fn as_id(&self) -> Option<Id> {
+        match self {
+            FastmailMaskedEmailValue::Id(id) => Some(*id),
+            _ => None,
+        }
+    }
+
+    fn as_any_id(&self) -> Option<AnyId> {
+        match self {
+            FastmailMaskedEmailValue::Id(id) => Some(AnyId::Id(*id)),
+            _ => None,
+        }
+    }
+
+    fn as_id_ref(&self) -> Option<&str> {
+        None
+    }
+
+    fn try_set_id(&mut self, new_id: AnyId) -> bool {
+        if let AnyId::Id(id) = new_id {
+            *self = FastmailMaskedEmailValue::Id(id);
+            true
+        } else {
+            false
+        }
+    }
+}
+
+impl JmapObjectId for FastmailMaskedEmailProperty {
+    fn as_id(&self) -> Option<Id> {
+        None
+    }
+
+    fn as_any_id(&self) -> Option<AnyId> {
+        None
+    }
+
+    fn as_id_ref(&self) -> Option<&str> {
+        None
+    }
+
+    fn try_set_id(&mut self, _: AnyId) -> bool {
+        false
+    }
+}

crates/jmap-proto/src/object/mod.rs

@@ -18,6 +18,7 @@ pub mod calendar_event_notification;
 pub mod contact;
 pub mod email;
 pub mod email_submission;
+pub mod fastmail_masked_email; // inbuxa: masked email
 pub mod file_node;
 pub mod identity;
 pub mod mailbox;