Add a note on email encodings

Leave a note for future devs that the server might receive an email with
an encoding different from ASCII or UTF-8. This can be problematic as
String accepts only UTF-8 valid strings.

In TODO when I say "handle non UTF-8 encodings", I think it would be
totally ok to just disregard anything that isn't UTF-8 and return a
"rejected for policy" error to the MTA. Otherwise we'll just have to put
`encoding_rs` in the mix.

Signed-off-by: Mroik <mroik@delayed.space>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/smtp_server.rs b/src/smtp_server.rs
index 2805081..b4f59db 100644
--- a/src/smtp_server.rs
+++ b/src/smtp_server.rs
@@ -85,6 +85,13 @@ impl SessionHandler {
 
         loop {
             buffer.clear();
+            // Technically emails could use any arbitrary encoding, not necessarily ASCII or UTF-8.
+            // If such encoding is ever encountered it would error on this line.
+            //
+            // For now we won't bother to check as it is unlikely, but it should be handled before
+            // deploying in production.
+            //
+            // TODO: Handle non UTF-8 encoding.
             if reader.read_line(&mut buffer).await? == 0 {
                 break;
             }