Fix issues

bin/nexusbot.dart

@@ -76,18 +76,19 @@ void main(List<String> argsRaw) async {
           "✉️ Sending...",
         );
 
-        final from = mail.MailAddress(settings.mailName, settings.email);
-        final mailClient = await container.read(
-          MailClientController.provider.future,
-        );
-        await mailClient.sendMessageBuilder(
-          mail.MessageBuilder.prepareMultipartAlternativeMessage(
-            plainText:
-                """Your registration for Federated Nexus has been accepted! Your credentials are:
+        await container
+            .read(MailClientController.provider.notifier)
+            .sendMessage(
+              plainText:
+                  """Your registration for Federated Nexus has been accepted! Your credentials are:
 Username: ${registration.username}.
-Password: $password""",
-            htmlText: markdownToHtml(
-              """# Your registration for Federated Nexus has been accepted!
+Password: $password
+
+If you have any questions, check out our documentation: https://federated.nexus/services/matrix/.
+
+If you have any issues, reply to this email.""",
+              markdown:
+                  """# Your registration for Federated Nexus has been accepted!
 ## Your credentials are:
 - ### Username: ${registration.username}.
 - ### Password: $password
@@ -95,14 +96,11 @@ Password: $password""",
 If you have any questions, check out [our documentation](https://federated.nexus/services/matrix/).
 
 If you have any issues, reply to this email.""",
-            ),
-          )..subject = "Your registration for Federated Nexus has been accepted!",
-          from: from,
-          recipients: [
-            mail.MailAddress(registration.username, registration.email),
-          ],
-        );
-
+              subject:
+                  "Your registration for Federated Nexus has been accepted!",
+              from: mail.MailAddress(settings.mailName, settings.email),
+              to: mail.MailAddress(registration.username, registration.email),
+            );
         await event.room.redactEvent(reactionEvent!);
         await event.room.sendReaction(event.eventId, "✉️ Sent!");
     }
@@ -114,7 +112,9 @@ If you have any issues, reply to this email.""",
         (Router()..post("/", (Request request) async {
               final body = await request.readAsString();
               final registration = Registration.fromJson(
-                Uri.splitQueryString(body),
+                Uri.splitQueryString(
+                  body,
+                ).map((key, value) => MapEntry(key, value.toLowerCase())),
               );
 
               final client = await container.read(