Remove unused unstable feature
@@ -68,7 +68,6 @@ file-transport = ["serde", "serde_json"]
rustls-tls = ["webpki", "webpki-roots", "rustls"]
sendmail-transport = []
smtp-transport = ["base64", "nom"]
-unstable = []
[package.metadata.docs.rs]
all-features = true
