If you send a lot of emails on a regular basis, you are probably aware of email authentication methods like DKIM, SPF, and DMARC. Several problems may occur when implementing these protocols for your domain. If not addressed quickly, these will be rendered ineffective and will provide no protection.
In this blog, we’ll be discussing one of the most prevalent errors faced by users with SPF implemented on their domains: Too many DNS lookups.
But for those unfamiliar with what SPF is,
here’s a refresher.
SPF (Sender
Policy Framework)
Sender Policy Framework, like DKIM, is an
email authentication protocol that enables domain owners to designate which
email servers are allowed to send emails from their domain or domains.
SPF detects fraudulent sender addresses when
the email is being sent. It is restricted, however, to identifying a forged
sender claim in the email’s envelope, which is used when the email bounces.
When used in conjunction with DMARC, SPF detects email spoofing, a typical
phishing scheme in which the email address or domain name of a reputable firm
or trusted acquaintance is used.
Ways to Avoid SPF failures
The SPF specification restricts the number of
DNS lookups to a maximum of ten. This restriction helps mailbox providers use
fewer resources while verifying SPF data. If you surpass this limit, the SPF
check will fail. A DNS lookup necessitates the mailbox provider to request
information for a domain from the DNS, resulting in longer processing times and
the usage of additional computer resources.
So what measures can be taken to avoid
reaching the DNS limit? We’ve got SIX for you!
- Use lesser
INCLUDE statements
An include statement is a method in your SPF
record that sends DNS lookups to another domain’s SPF record in order to
validate any of their permitted IPs. Each include statement in the originating
SPF record and any SPF records pointed to counts toward the maximum of ten.
Also Read:- How are DMARC, DKIM and SPF different
from each other?
You must also verify that each include
statement in your SPF record is relevant and absolutely cannot be substituted
by another method such as the ip4 and ip6 mechanisms.
- Implement
ip4 and ip6 mechanisms
When you have the opportunity, replace your
include statement with the ip4 or ip6 mechanism to minimize the number of DNS
lookups. To specify a static IP range in your SPF record, utilize the ip4 and
ip6 methods. This negates the requirement for an include statement, which
refers to the SPF record of another domain, thus helping you avoid going over
the lookup limit.
- Avoid
resolving to the same domain
Remove any mechanisms from your SPF record
that resolve to the same domain to minimize needless DNS lookups.
- Avoid ptr
Mechanisms
The SPF standard advises against using the ptr
method in your SPF record. The ptr mechanism is a DNS record that maps an IP
address to a domain or hostname. You should avoid utilizing this method since
it might result in a high number of DNS lookups, leading to the limit of 10
being exceeded.
- Remove
Unnecessary Vendor Domains
Include statements are used by senders to direct
the SPF check to a vendor or partner’s SPF record as their IP addresses
frequently change. Using a partner’s or vendor’s include statement relieves the
sender of the need to constantly update those changing IP ranges in their own
SPF record.
- Reference to
Domains That are Currently Active
You should ensure that the domains you mention
truly resolve to an active SPF record. If they don’t, they should be deleted.
These six pointers will help you avoid any
unnecessary errors that might pop up while implementing SPF for your domain.
Another thing to keep in mind is to avoid using incorrect syntax while
deploying SPF. If you want to verify and check your newly created SPF record,
use our free SPF record checker tool now!
Source Content:- https://medium.com/@EmailAuth/6-ways-to-avoid-spf-failures-if-you-are-reaching-the-dns-lookup-limit-e703ce1acf1f