Looks like the smtp settings in the appserver are not correct.
Usually you get an error like SMTP sendMail failed (server: smtpdomain.com:25)
Your error looks like there is no SMTP server defined:
SMTP sendMail failed (server: 0)
Have someone check the appserver for the smtp settings.
I had the same issue with SMTP error.
Open the appserver and process scheduler config files and look for SMTPSender=
Valid that is an existing and valid email address on both config files.