Tengo el mismo problema en moodle 3
xxxx@yahoo.es
host mx-eu.mail.am0.yahoodns.net [188.125.69.79]
SMTP error from remote mail server after end of data:
554 5.7.9 Message not accepted for policy reasons. See https://help.yahoo.com/kb/postmaster/SLN7253.html
Action: failed
Final-Recipient: xxxxxx@yahoo.es
Status: 5.0.0
Remote-MTA: dns; mx-eu.mail.am0.yahoodns.net
Diagnostic-Code: smtp; 554 5.7.9 Message not accepted for policy reasons. See https://help.yahoo.com/kb/postmaster/SLN7253.html
