There are many issues that you might run into when trying to set up an SPF record for your domain. Below we've listed some of the common issues with tips on how to move forward.
More than One SPF Record
Having multiple SPF records can cause conflicts and lead to email delivery issues. SPF records are used to specify which servers are authorized to send emails on behalf of your domain. If you have multiple SPF records, it can create confusion for receiving mail servers and result in SPF failures. It is important to carefully manage and consolidate your SPF records to ensure proper email authentication and delivery.
What to Do:
If you have more than one SPF record, consolidate them into a single record. For example:
- v=spf1 a mx include:_spf.google.com include:spf.protection.outlook.com ~all
- v=spf1 a mx include:sendgrid.net ~all
Combine the record into a single instance:
- v=spf1 a mx include:_spf.google.com include:spf.protection.outlook.com include:sendgrid.net ~all
Maximum of 10 Lookups
There are a few reasons why there is a maximum limit of 10 lookups in an SPF record. Firstly, having too many lookups can significantly impact the performance of DNS resolution. Secondly, it helps to prevent potential loops or infinite recursion in the DNS lookup process. Lastly, limiting the number of lookups encourages organizations to keep their SPF records concise and efficient.
What to Do:
Identify the services in your SPF record, if there are any no longer used services, remove them. In some instances, services will get around this by "SPF Flattening", listing allowed IPs instead of using SPF lookups. This can be useful, but has the negative that it needs to be updated whenever any service you use adds or adjusts IP addresses.
Syntax Issues
There are a few common syntax issues that can occur with SPF records such as not including the necessary v=spf1 prefix at the beginning of the record. The second is not properly separating multiple mechanisms with spaces or using incorrect syntax for modifiers.
Some other examples include:
- Missing "include" mechanism - Make sure all referenced domains and their include mechanisms are present.
- Misspellings or typos in common mechanisms: v=sfp1, includ:, al, etc - Fix any misspellings in the domains or any mechanisms
- Text after the closing "~all" text - The last item in your SPF record should be the ~all text
- Extra characters such as commas in the record - The record should contain the mechanisms each separated with a comma and no more.
- Starting the record with an opening parenthesis - The first information should be: v=spf1
Too Permissive of an "all" mechanism
The goal of SPF is to ensure that only your authorized servers can send on your domain's behalf. By using "?all" or "+all" in your records, you would be setting a neutral or open policy toward *all* senders.
What to Do:
Using a more restrictive policy such as "~all" will ensure that emails from unauthorized senders "spoofing" your domain don't successfully impersonate you.