Customers using the email relay might discover that emails are not being delivered to Office 365 accounts, even though they may be received by people with email addresses not using Office 365.
This is usually because of a feature of Office 365 as well as many other email systems called the Sender Protection Framework (SPF).
The SPF system has a special set of instructions (called an SPF record) added to the domain name (DNS) entry for a given domain and details those machines, domains and IP addresses which are allowed to send email for that domain.
Microsoft, when using Office 365 advise that the SPF record for a domain should follow a format such as:
v=spf1 include:spf.protection.outlook.com include:spf.exclaimer.net ~all
See the Microsoft help topic, Set up SPF in Office 365 to help prevent spoofing. Because the Smoothwall’s hostname or IP address is not listed in this record, the emails sent by the Smoothwall fail to deliver.
Set the report output settings for this SMTP server, see our help topic, Configuring report output settings:
- SMTP server: 127.0.0.1
The sender's email address should be a real email address which can receive emails and is from the same domain used for Office 365
Amending SPF records for Office 365
The externally hosted DNS record for the domain (such as example.com) should be amended to include an entry which includes the External IP address of the Smoothwall. The Microsoft article linked in this document contains instructions on how to do so.
This configuration will not only allow the Smoothwall to send emails, but will instruct Office 365 (and any other systems which check the SPF record) to verify that the external IP addresses are allowed to send emails on behalf of that domain.