Alternative for tokio-graceful-shutdown (#108)

* Replace tokio-graceful-shutdown with cancellation tokens
* Update axum, rustls, rcgen and tower
* Fix for dark mode

README.md

@@ -94,7 +94,7 @@ The web interface will also be served at [http://localhost:1080/emails/](http://
 
 ### Reverse proxy
 
-See [the reverse proxy guide](./Reverse_proxy.md).
+See [the reverse proxy guide](./reverse_proxy.md).
 
 ### Retention period
 
@@ -143,6 +143,14 @@ cd backend/
 cargo test send_sample_messages -- --ignored
 ```
 
+Alternatively you can send messages using curl:
+
+```sh
+curl smtp://127.0.0.1:1025 --mail-from [email protected] --mail-rcpt [email protected] --upload-file samples/normal.email --user 'user:pass'
+# with tls
+curl -k --ssl-reqd smtps://127.0.0.1:1025 --mail-from [email protected] --mail-rcpt [email protected] --upload-file samples/normal.email --user 'user:pass'
+```
+
 ## Development
 
 Install [Rust](https://www.rust-lang.org/learn/get-started) and [Trunk](https://trunkrs.dev/)