Software Spam emails "Mail Delivery System" , Virgin letter

[silverdale]

So over the past week I noticed I was getting an awful lot of spam "Mail Delivery System" " WARNING, delayed for 72 hours" mail to my virgin address in Outlook so I deleted them. This morn I get a letter from Virgin saying your email is spamming etc .... please scan. I scanned and found 2 unsavory bits of crap and deleted them then after I went to my virgin account and changed my password for my email.
I thought that would be then end of it till I just received 2 more of these dodgy emails, is there something else I need to do ?