Downloads not mailing out about various executions

Since some good days ago, we have stopped receiving mails from download.moodle.org

This affects a number of utilities running there (packaging utilities, various selfupdate repositories, plugin webservices...).

Have tried to manually send something from there (business.srv):

echo "Hi, Eloy here!" | mailx -s "This is a test, ignore me" eloy@moodle.com

And nothing arrived. Then, looking to the queue... it seems that there is a problem there:

(delivery temporarily suspended: connect to art.srv.in.moodle.com[78.46.57.7]:25: Connection refused)

It would be great to get mailouts from downloads working, we need them to know when this or that (package, error...) has happened.

Ciao