I have a customer ABC Ltd (abc.ie) who has a requirement to send emails via SMTP to their own customer base from within an application that we have developed for them.
For their company email they use Office 365, i.e. hosted Exchange. Due to the recipient rate limits imposed on sending through that with SMTP, we are looking at using Mandrill instead. So it would be emails from '[email protected]' sent via Mandrill's SMTP.
Obviously we want to set up SPF and DKIM as per Mandrill recommendations. However I am confused as to where this configuration is done. Is the SPF/DKIM change done on the abc.ie hosted Exchange server even though mail is going nowhere near it?
You make the SPF/DKIM changes with your DNS provider.
Mandrill will tell you what entries to add to your DNS records when you do the DKIM and DNS verification step.
Since you already have O365, Mandrill will take those records into account and provide a full SPF TXT record that includes everything you'll need.