Fix clippy warnings (#967)

Cargo.toml

@@ -123,6 +123,9 @@ tokio1-boring-tls = ["tokio1", "boring-tls", "dep:tokio1_boring"]
 
 dkim = ["dep:base64", "dep:sha2", "dep:rsa", "dep:ed25519-dalek"]
 
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(lettre_ignore_tls_mismatch)'] }
+
 [package.metadata.docs.rs]
 all-features = true
 rustdoc-args = ["--cfg", "docsrs", "--cfg", "lettre_ignore_tls_mismatch"]

src/transport/mod.rs

@@ -12,7 +12,7 @@
 //!
 //! * a service from your Cloud or hosting provider
 //! * an email server ([MTA] for Mail Transfer Agent, like Postfix or Exchange), running either
-//! locally on your servers or accessible over the network
+//!   locally on your servers or accessible over the network
 //! * a dedicated external service, like Mailchimp, Mailgun, etc.
 //!
 //! In most cases, the best option is to: