In my previous blog I showed you how I implemented Trend Micro Hosted Email Security (HES) in my Exchange 2010 environment. Interesting case, it’s an Exchange 2010 hybrid environment with mailboxes in on-premises Exchange 2010 as well as mailboxes in Exchange Online. Centralized mail transport is used, so mail to and from Office 365 always routes via HES and the on-premises Exchange 2010 servers to Exchange Online. In this blog I will focus on implementing SPF, DKIM and DMARC in Trend Micro Hosted Email Security.
SPF in itself is covered in more detail in a previous blog post “SenderID, SPF, DKIM and DMARC in Exchange 2016 – Part I” which can be found here: https://jaapwesselius.com/2016/08/19/senderid-spf-dkim-and-dmarc-in-exchange-2016-part-i/.
In this scenario, mail from the inframan.nl domain (including Office 365) is only routed via the Hosted Email Security environment so the SPF record is pretty simple:
v=spf1 include:spf.hes.trendmicro.com ~all
Set this TXT record in your public domain, start sending email and when checking the header information you’ll see your all good here:
DKIM is a little more work to configure and takes a bit more time. DKIM is covered more in detail in part II of a previous series “SenderID, SPF, DKIM and DMARC in Exchange 2016 – Part II” which can be found here: https://jaapwesselius.com/2016/08/22/senderid-spf-dkim-and-dmarc-in-exchange-2016-part-ii/
DKIM is about signing header information using a private key, and to decipher the signature you need a public key which is stored in public DNS, accessible for every mail server on the Internet. No need to worry about the configuration, HES will deliver all the details.
In the HES console select Outbound Protection and select DomainKeys Identified Mail (DKIM) Signing.