Cron error, every day at 12:00 am sharp.

Cron <skyforum@serverxxxxx> env php -q /var/www/vhosts/xxxxxxx.net/xxxxxxxx/periodic/cron.php

SMTP Error: Data not accepted.

 Since the periodic report is generated at the same time and emailed to me, it stands to reason they are connected to this error somehow...

I don;t understand what could be causing it. Started when I moved servers.....

Are you running the SMTP mailer module? If so, have you updated the SMTP setting to match the new host?

Yes and yes. smtp mailer is working fine as well as all other emails on the site....