fix: ignore address case when comparing the To: field to Autocrypt-Gossip:

src/mimeparser.rs

@@ -1752,7 +1752,7 @@ async fn update_gossip_peerstates(
             .handle_fingerprint_change(context, message_time)
             .await?;
 
-        gossiped_addr.insert(header.addr.clone());
+        gossiped_addr.insert(header.addr.to_lowercase());
     }
 
     Ok(gossiped_addr)

src/receive_imf.rs

@@ -2211,7 +2211,7 @@ async fn check_verified_properties(
         let peerstate = Peerstate::from_addr(context, &to_addr).await?;
 
         // mark gossiped keys (if any) as verified
-        if mimeparser.gossiped_addr.contains(&to_addr) {
+        if mimeparser.gossiped_addr.contains(&to_addr.to_lowercase()) {
             if let Some(mut peerstate) = peerstate {
                 // if we're here, we know the gossip key is verified:
                 // - use the gossip-key as verified-key if there is no verified-key

src/securejoin.rs

@@ -583,7 +583,7 @@ pub(crate) async fn observe_securejoin_on_other_device(
             let addr = Contact::load_from_db(context, contact_id)
                 .await?
                 .get_addr()
-                .to_string();
+                .to_lowercase();
             if mime_message.gossiped_addr.contains(&addr) {
                 let mut peerstate = match Peerstate::from_addr(context, &addr).await? {
                     Some(p) => p,