Try all MX servers of destination domain

I would helpfull to tell swaks to try **all** MX records of the destination domain.
Currently it aborts if the first (lowest) MX server is down or refuses the connection.
I know I can force it via "-s dedicated-server.example.com" but I am thinking of just specifiing
"-t [foobar@example.com](mailto:foobar@example.com)" without dig-ing for the MX records first.

Background info:
I am using swaks to verify a (big) bunch of external forwarding addresses with the "--quit-after RCPT "
switch and currently it fails, if the first MX of the destination domain is down or busy.
So a switch like "--try-all-MX" would be helpfull. Maybe together with a timeout parameter "--MX-timeout "

Start by reading swaks's handling of the -t destination and --quit-after RCPT, then trace how the destination domain's first MX server is selected and connection failures are handled. Define the expected behavior for trying all MX records, including the proposed --try-all-MX and --MX-timeout options, and verify that forwarding-address checks continue when one MX server is unavailable.

Written by the indexing model from the issue text.