Why Does ImprovMX Need SPF?

The Sender Policy Framework (SPF) is a DNS-based mechanism that authorizes services to send emails on behalf of a domain. ImprovMX requires SPF configuration for specific technical reasons related to email forwarding and bounce handling.

The Main Reason: Bounce Handling

When ImprovMX forwards emails, we need to know whether messages successfully reached their final destination. This information arrives via bounce notifications sent to the return path address specified in the MAIL FROM command during the SMTP transaction.

Here's the technical challenge:

If ImprovMX used the original sender's email address in the MAIL FROM field, receiving servers might reject the message (since we're not listed in that sender's SPF records)
Since your domain's email is managed by ImprovMX, it's more practical to add ImprovMX to your SPF records
This allows ImprovMX to set the MAIL FROM domain to yours
Receiving servers then send bounce reports back to your domain, which ImprovMX can process appropriately

Your SPF Record

Add this TXT record to your DNS:

v=spf1 include:spf.improvmx.com ~all

If you already have an SPF record, merge the ImprovMX include with your existing record. For example:

v=spf1 include:spf.improvmx.com include:_spf.google.com ~all

DMARC and Domain Alignment

DMARC verification ensures senders are authorized by validating SPF and DKIM alignment with the sender's domain. When ImprovMX uses the recipient's email as the return path instead of the sender's, SPF validation remains intact, but domain alignment might be affected.

This issue only occurs when an email:

Contains DMARC records, but
Lacks DKIM signatures

In such cases, ImprovMX's servers rewrite the sender information to maintain compliance. However, most domains implementing DMARC already include DKIM, making this scenario relatively uncommon.

Learn More

For more details on email authentication: