Problem

How to create a Sender Policy Framework (SPF) Record to Authorise outMail Servers to send out your Email?

Solution

Although not essential it can help make email delivery more reliable if you create a SPF record for your domain name. This DNS record is to comply with the Sender Policy Framework (SPF) anti-spam initiative and it identifies outMail servers as being approved for sending emails from your domain.

It's a TXT record, which not all DNS servers or ISP control panels can handle, but if they can this is the record you need to add or modify:-

example.com.   IN   TXT     "v=spf1 include:spf.smtp-engine.com -all"

This is how it should appear in your DNS Zone File, including the inverted commas, but with your domain name substituted for example.com.

If you already have an SPF record, the key change required is to insert include:spf.smtp-engine.com before the -all, this will ensure that the outmail records are checked.

If you already have an SPF record

Most domains already have an SPF record configured, especially if you use services such as Microsoft 365, Google Workspace, or a website hosting provider.

It is important that you do not create multiple SPF records for the same domain, as this will cause SPF checks to fail.

Instead, you must update your existing SPF record to include the outMail servers.

Example

If your current SPF record looks like this:

example.com.   IN   TXT     "v=spf1 include.protection.outlook.com -all"

You should modify it to include outMail, for example:

example.com.   IN   TXT     "v=spf1 include.protection.outlook.com include.outmail.example -all"

This ensures both services are authorised to send email on behalf of your domain.

SPF lookup limits (10 DNS lookup rule)

SPF records have a limit of 10 DNS lookups. This includes all "include", "a", "mx", and "redirect" mechanisms.

If your SPF record exceeds this limit, SPF validation will fail, which can result in email delivery problems.

Tips to avoid SPF lookup issues:

• Remove unused or duplicate include statements
• Avoid chaining too many third-party services
• Use SPF flattening if necessary
• Regularly review your SPF record as services change

If you are unsure, it is recommended to review your SPF configuration carefully before making changes.

Common SPF record issues

Multiple SPF records

Only one SPF record is allowed per domain. Having more than one will cause SPF checks to fail.

Missing include statement

If outMail is not included in your SPF record, emails sent through it may fail SPF checks.

Incorrect syntax

SPF records must be formatted correctly. Even small errors can invalidate the record.

Changes not taking effect

DNS updates can take time to propagate. Allow up to 24 hours for changes to apply.