add umbrella crate

email/src/error.rs

@@ -0,0 +1,11 @@
+use viendesu_core::{errors::Aux, mk_error};
+
+pub type MailResult<O> = Result<O, MailError>;
+
+mk_error!(MailError);
+
+impl From<MailError> for Aux {
+    fn from(value: MailError) -> Self {
+        Self::Mail(eva::str::format_compact!("{}", value.0))
+    }
+}