The construction of an EventHandler object should not be directly done
by the client. Instead, it is easier to use procedural macro to
automatize the process, hence exposing a nice and simple interface. Such
use of procedural macros requires to crate an additional crate.
The latest OpenSMTPD draft added the timeout event, it therefore has
been added to the parser. As shown in the new sessions examples, the
timestamp format changed and the parameters are also optional.
