We had a lead fill out a form, which triggered an automatic follow-up email. However, the follow-up email bounced, and this is the note that was in the lead's Marketo activity:
554- 554 Unfortunately your access to this mail system has been rejected due to the sending MTA's poor reputation and e-mail hygiene on the Internet. Please reference the following URL for more information: http://www.senderbase.org/search?searchString=220.127.116.11
Anyone have more information on this?