If you want to use the Workbooks servers to send your outbound emails then we would suggest you setup your SPF records in DNS so that the Workbooks servers are recognised as a valid source of email for your domain.  This will reduce the likelihood that your email is blocked as spam.

Your IT team or company that manages your DNS records can help with the configuration.  They need to add something called the TXT record to DNS.  The details are below:

TXT "v=spf1 ip4:80.69.20.160/28 ip4:89.187.105.224/28 mx ~all"