Has the ihug email system been hacked ?
https://community.vodafone.co.nz/t5/My-Vodafone-more/email-ihug/m-p/169494
This looks exactly like whats happended to one of my customers. Lots of bouncebacks , laptop is clean (or an undectable virus). no obvious sign of spam email beinmg sent from laptop.
I now have another customer, ihug/voda just informed them their a/c has been spamming.
About to check that one soon, I'll bet its also clean