HELP: Gmail labeling Zoho Campaigns emails to spam: "We've found that lots of messages from zcsend.net are spam"

HELP: Gmail labeling Zoho Campaigns emails to spam: "We've found that lots of messages from zcsend.net are spam"

Since yesterday all my emails from Zohocampaigns seem to end up in spam ... I even sent two to my gmail address and they went to spam. At the top of the email in my spam folder it says: 
Why is this message in Spam?  We've found that lots of messages from zcsend.net are spam
What can you do to rectify this ASAP?