Hello, 

My Zoho Campaign test messages are marked by a filter as spam in Outlook, but not in Gmail. 

The header appears to be sent by (I've omitted my email address):  

... =[domain name]@zcsend.net; on behalf of Matt from Plural <[my email address]>; ( ... =[domain name] via zcsend.net)

The error message on the Outlook message is:

".... This message was marked as spam using a junk filter other than the Outlook Junk Email filter. We could not verify the identity of the sender. Click here to learn more." 

This leads to this article:

"Identify suspicious messages in Outlook.com and Outlook on the web"

In Zoho CRM and Zoho Campaigns, I set up SPF and DKIM verfication described here, and I believe it is working:

What steps can I take to reduce the likelihood this is flagged as spam?