diff --git a/crates/features/src/masked_email/ops.rs b/crates/features/src/masked_email/ops.rs
index fafc961..82af2c3 100644
--- a/crates/features/src/masked_email/ops.rs
+++ b/crates/features/src/masked_email/ops.rs
@@ -333,6 +333,19 @@ pub async fn ensure_indexed(data: &Store, registry: &RegistryStore) -> trc::Resu
     data.write(batch.build_all()).await.map(|_| ())
 }
 
+/// Whether an account may send as an address because it's one of the
+/// account's live masks (ME-11).
+pub async fn sends_as(
+    data: &Store,
+    registry: &RegistryStore,
+    account_id: u32,
+    address: &str,
+) -> trc::Result<bool> {
+    Ok(resolve(data, registry, address)
+        .await?
+        .is_some_and(|mask| mask.object.account_id.document_id() == account_id))
+}
+
 /// What an address is, as far as masks go.
 #[derive(Debug)]
 pub enum Lookup {
diff --git a/crates/jmap/src/identity/set.rs b/crates/jmap/src/identity/set.rs
index f52cd71..3a542a5 100644
--- a/crates/jmap/src/identity/set.rs
+++ b/crates/jmap/src/identity/set.rs
@@ -75,6 +75,14 @@ impl IdentitySet for Server {
                     .addresses()
                     .iter()
                     .any(|e| e == &identity.email)
+                    // inbuxa: ME-11: a live mask of the account's own is an identity too
+                    && !inbuxa_features::masked_email::ops::sends_as(
+                        &self.core.storage.data,
+                        self.registry(),
+                        account_id,
+                        &identity.email,
+                    )
+                    .await?
                 {
                     response.not_created.append(
                         id,
diff --git a/crates/smtp/Cargo.toml b/crates/smtp/Cargo.toml
index 2bdd6b7..1581c7a 100644
--- a/crates/smtp/Cargo.toml
+++ b/crates/smtp/Cargo.toml
@@ -18,6 +18,7 @@ directory = { path =  "../directory" }
 common = { path =  "../common" }
 email = { path =  "../email" }
 registry = { path =  "../registry" }
+inbuxa-features = { path = "../features" }
 spam-filter = { path =  "../spam-filter" }
 trc = { path = "../trc" }
 mail-auth = { version = "0.13", features = ["rkyv"] }
diff --git a/crates/smtp/src/inbound/mail.rs b/crates/smtp/src/inbound/mail.rs
index 482f191..332d622 100644
--- a/crates/smtp/src/inbound/mail.rs
+++ b/crates/smtp/src/inbound/mail.rs
@@ -248,6 +248,15 @@ impl<T: SessionStream> Session<T> {
                         .authenticated_emails()
                         .iter()
                         .any(|e| e == address_lcase)
+                    // inbuxa: ME-11: the sender's own live masks are its addresses too
+                    && !inbuxa_features::masked_email::ops::sends_as(
+                        &self.server.core.storage.data,
+                        self.server.registry(),
+                        self.data.authenticated_as.as_ref().unwrap().account_id,
+                        address_lcase,
+                    )
+                    .await
+                    .unwrap_or(false)
                 {
                     trc::event!(
                         Smtp(SmtpEvent::MailFromUnauthorized),