And as usual, the answer is not as straightforward as we think. SPF determines whether or not a sender is permitted to send on behalf of a domain. As of October 2018, spoof intelligence is available to all organizations with mailboxes in Exchange Online, and standalone EOP organizations without Exchange Online mailboxes. This is the default value, and we recommend that you don't change it. See Report messages and files to Microsoft. It is published as a Domain Name System (DNS) record for that domain in the form of a specially formatted TXT record. For example, exacttarget.com has created a subdomain that you need to use for your SPF TXT record: When you include third-party domains in your SPF TXT record, you need to confirm with the third-party which domain or subdomain to use in order to avoid running into the 10 lookup limit. The Microsoft 365 Admin Center only verifies if include:spf.protection.outlook.com is included in the SPF record. It can take a couple of minutes up to 24 hours before the change is applied. There are many free, online tools available that you can use to view the contents of your SPF TXT record. Periodic quarantine notifications from spam and high confidence spam filter verdicts. In case we want to get more information about the event or in case we need to deliver the E-mail message to the destination recipient, we will have the option. One option that is relevant for our subject is the option named SPF record: hard fail. Neutral. After a specific period, which we allocate for examining the information that collected, we can move on to the active phase, in which we execute a specific action in a scenario that the Exchange rule identifies an E-mail message that is probably Spoof mail. In this phase, we will need to decide what is the concrete action that will apply for a specific E-mail message that will identify a Spoof mail (SPF = Fail). What is the recommended reaction to such a scenario? The E-mail address of the sender uses the domain name of a well-known bank. Figure out what enforcement rule you want to use for your SPF TXT record. SPF discourages cybercriminals from spoofing your domain, spam filters will be less likely to blacklist it. To fix this issue, a sender rewriting scheme is being rolled out in Office 365 that will change the sender email address to use the domain of the tenant whose mailbox is forwarding the message. What does SPF email authentication actually do? Although there are other syntax options that are not mentioned here, these are the most commonly used options. Given that we are familiar with the exact structure of our mail infrastructure, and given that we are sure that our SPF record includes the right information about our mail servers IP address, the conclusion is that there is a high chance that the E-mail is indeed spoofed E-mail! Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type. SPF sender verification test fail | External sender identity. Creating multiple records causes a round robin situation and SPF will fail. Vs. this scenario, in a situation in which the sender E-mail address includes our domain name, and also the result from the SPF sender verification test is fail, this is a very clear sign of the fact that the particular E-mail message has a very high chance to consider as Spoof mail. A4: The sender E-mail address, contains information about the domain name (the right part of the E-mail address). Links to instructions on working with your domain registrar to publish your record to DNS are also provided. The following Mark as spam ASF settings set the SCL of detected messages to 9, which corresponds to a High confidence spam filter verdict and the corresponding action in anti-spam policies. If you have a hybrid configuration (some mailboxes in the cloud, and some mailboxes on premises) or if you're an Exchange Online Protection standalone customer, add the outbound IP address of . If you don't use a custom URL (and the URL used for Office 365 ends in onmicrosoft.com), SPF has already been set up for you in the Office 365 service. In order to use a custom domain, Office 365 requires that you add a Sender Policy Framework (SPF) TXT record to your DNS record to help prevent spoofing. Although SPF is designed to help prevent spoofing, but there are spoofing techniques that SPF can't protect against. ip4 indicates that you're using IP version 4 addresses. Disabling the protection will allow more phishing and spam messages to be delivered in your organization. This phase can describe as the active phase in which we define a specific reaction to such scenarios. Failing SPF will not cause Office 365 to drop a message, at best it will mark it as Junk, but even that wont happen in all scenarios. Fix Your SPF Errors Now SPF Check Path The path for the check is as follows Exchange Admin Center > Protection > Spam Filter > Double Click Default > Advanced Options > Set SPF record: Hard fail: Off One of the prime reasons why Office 365 produces a validation error is an invalid SPF record. SPF is added as a TXT record that is used by DNS to identify which mail servers can send mail on behalf of your custom domain. . Messages that contain hyperlinks that redirect to TCP ports other than 80 (HTTP), 8080 (alternate HTTP), or 443 (HTTPS) are marked as spam. For example, one of the most popular reasons for the result fail when using the SPF sender verification test is a problem or a miss configuration, in which the IP address of one of our mail server/services that our organization use, was not added to the SPF record. Did you know you can try the features in Microsoft 365 Defender for Office 365 Plan 2 for free? This record probably looks like this: If you're a fully hosted customer, that is, you have no on-premises mail servers that send outbound mail, this is the only SPF TXT record that you need to publish for Office 365. If you're already familiar with SPF, or you have a simple deployment, and just need to know what to include in your SPF TXT record in DNS for Microsoft 365, you can go to Set up SPF in Microsoft 365 to help prevent spoofing. The 6 commonly used elements in an SPF record are: You can add as many include: or ip4: elements to your SPF record as you need. Hope this helps. The -all rule is recommended. As mentioned, in an Exchange-based environment, we can use the Exchange rule as a tool that will help us to capture the event of SPF = Fail and also, choose the required response to such an event. Your email address will not be published. A5: The information is stored in the E-mail header. Outlook.com might then mark the message as spam. One option that is relevant for our subject is the option named SPF record: hard fail. Some online tools will even count and display these lookups for you. For advanced examples, a more detailed discussion about supported SPF syntax, spoofing, troubleshooting, and how Office 365 supports SPF, see How SPF works to prevent spoofing and phishing in Office 365. In the current article, I want to provide you with a useful way, to implement a mail security policy related to an event in which the result of the SPF sender verification check is Fail. If we want to be more precise, an event in which the SPF sender verification test result is Fail, and the sender used the E-mail address, which includes our domain name. Note: Suppose we want to be more accurate, this option is relevant to a scenario in which the SPF record of the particular domain is configured with the possibility of SPF hard fail. One drawback of SPF is that it doesn't work when an email has been forwarded. Learn about who can sign up and trial terms here. - last edited on Default value - '0'. On-premises email organizations where you route. Its a good idea to configure DKIM after you have configured SPF. Edit Default > advanced optioins > Mark as Spam > SPF record: hard fail: Off. For more information, see Advanced Spam Filter (ASF) settings in EOP. A3: To improve the ability of our mail infrastructure, to recognize the event in which there is a high chance, that the sender spoofs his identity or a scenario in which we cannot verify the sender identity.The other purpose of the SPF is to protect our domain mane reputation by enabling another organization to verify the identity of an E-mail message that was sent by our legitimate users. The obvious assumption is that this is the classic scenario of Spoof mail attack and that the right action will be to block automatically or reject the particular E-mail message. Sender Policy Framework (SPF) allows email administrators to reduce sender-address forgery (spoofing) by specifying which are allowed to send email for a domain. The answer is that as always; we need to avoid being too cautious vs. being too permissive. For example, 131.107.2.200. The second one reads the "Authentication-Results" line in the header information and if it says "Fail" sends the email to quarantine. IT, Office365, Smart Home, PowerShell and Blogging Tips. For example: Previously, you had to add a different SPF TXT record to your custom domain if you were using SharePoint Online. The reason that I prefer the option of Exchange rule is, that the Exchange rule is a very powerful tool that can be used to define a Tailor-made SPF policy that will suit the specific structure and the needs of the organization. If you have a hybrid deployment (that is, you have some mailboxes on-premises and some hosted in Microsoft 365), or if you're an Exchange Online Protection (EOP) standalone customer (that is, your organization uses EOP to protect your on-premises mailboxes), you should add the outbound IP address for each of your on-premises edge mail servers to the SPF TXT record in DNS. The simple truth is that we cannot prevent this scenario because we will never be able to have control over the external mail infrastructure that is used by these hostile elements. SPF works best when the path from sender to receiver is direct, for example: When woodgrovebank.com receives the message, if IP address #1 is in the SPF TXT record for contoso.com, the message passes the SPF check and is authenticated. This is used when testing SPF. In reality, most of the organization will not implement such a strict security policy because they would prefer to avoid a false-positive scenario in which a legitimate mail mistakenly identified as Spoof mail. For example, in case that we need to Impose a strict security policy, we will not be willing to take the risk, and in such scenario, we will block the E-mail message, send the E-mail to quarantine or forward the E-mail to a designated person that will need to examine the E-mail and decide if he wants to release the E-mail or not. Q8: Who is the element which is responsible for alerting users regarding a scenario in which the result of the SPF sender verification test is Fail? Authentication-Results: spf=none (sender IP is 118.69.226.171) smtp.mailfrom=kien.ngan; thakrale5.onmicrosoft.com; dkim=none (message not signed) header.d=none;thakrale5.onmicrosoft.com; dmarc=none action=none header.from=thakrale5.onmicrosoft.com; Received-SPF: None (protection.outlook.com: kien.ngan does not designate permitted sender hosts) To be able to avoid from a false-positive event, meaning an event in which a legitimate E-mail message mistakenly identified as Spoof mail, I prefer more refinement actions such as send the E-mail to approval, send the E-mail to quarantine and so on. Messages that use JavaScript or Visual Basic Script Edition in HTML are marked as high confidence spam. A10: To avoid a scenario of false-positive meaning, a scene in which legitimate E-mail will mistakenly identify as a Spoof mail. The reason for the outcome of SPF = Fail is related to a missing configuration on the sending mail infrastructure., The E-mail address of the sender, uses the domain name of, The result from the SPF sender verification test is , The popular organization users who are being attacked, The various types of Spoofing or Phishing attacks, The E-mail address of the sender includes our domain name (in our specific scenario; the domain name is, The result of the SPF sender verification check is fail (SPF = Fail). If an SPF TXT record exists, instead of adding a new record, you need to update the existing record. When the receiving messaging server gets a message from joe@contoso.com, the server looks up the SPF TXT record for contoso.com and finds out whether the message is valid. Keeping track of this number will help prevent messages sent from your organization from triggering a permanent error, called a perm error, from the receiving server. Nearly all large email services implement traditional SPF, DKIM, and DMARC checks. If you set up mail when you set up Microsoft 365, you already created an SPF TXT record that identifies the Microsoft messaging servers as a legitimate source of mail for your domain. Each include statement represents an additional DNS lookup. For questions and answers about anti-spam protection, see Anti-spam protection FAQ. DMARC email authentication's goal is to make sure that SPF and DKIM information matches the From address. The Exchange incident report includes a summary of the specific mail flow, such as the name of the sender, recipient, and the Exchange rule that was activated and also; we can ask to include an attachment of the original E-mail message that was captured.. In reality, there is always a chance that the E-mail message in which the sender uses our domain name includes and the result from the SPF sender verification test is Fail could be related to some miss configuration issue. The enforcement rule is usually one of these options: Hard fail. For each ASF setting, the following options are available in anti-spam policies: On: ASF adds the corresponding X-header field to the message, and either marks the message as Spam (SCL 5 or 6 for Increase spam score settings) or High confidence spam (SCL 9 for Mark as spam settings). The meaning of the SPF = Fail is that we cannot trust the mail server that sends the E-mail message on behalf of the sender and for this reason, we cannot trust the sender himself. The enforcement rule indicates what the receiving mail system should do with mail sent from a server that isnt listed in the SPF record. In each of the above scenarios, the event in which the SPF sender verification test ended with SPF = Fail result is not good. Secondly, if your user has the sender's address added to their safe senders list, or sender address is in contacts + contacts are trusted, the message would skip spam filtering and be delivered to inbox. You add an SPF TXT record that lists the Office 365 messaging servers as legitimate mail servers for your domain. While there was disruption at first, it gradually declined. ASF specifically targets these properties because they're commonly found in spam. The main reason that I prefer to avoid the option of using the Exchange Online spam filter option is because, this option doesnt distinguish between a scenario in which the sender uses our domain name as part of his E-mail address vs. a scenario in which the sender uses E-mail address, which doesnt include our domain name. is required for every domain and subdomain to prevent attackers from sending email claiming to be from non-existent subdomains. You can't report messages that are filtered by ASF as false positives. Suppose a phisher finds a way to spoof contoso.com: Since IP address #12 isn't in contoso.com's SPF TXT record, the message fails the SPF check and the receiver may choose to mark it as spam. It is true that Office 365 based environment support SPF but its imperative to emphasize that Office 365 (Exchange Online and EOP) is not configured anything automatically! You can also subscribe without commenting. The element which needs to be responsible for capturing event in which the SPF sender verification test considered as Fail is our mail server or the mail security gateway that we use. The rest of this article uses the term SPF TXT record for clarity. This setting combines an SPF check with a Sender ID check to help protect against message headers that contain forged senders. Best practices and the latest news on Microsoft FastTrack, The employee experience platform to help people thrive at work, Expand your Azure partner-to-partner network, Bringing IT Pros together through In-Person & Virtual events. (Yahoo, AOL, Netscape), and now even Apple. Go to your messaging server(s) and find out the External IP addresses (needed from all on-premises messaging servers). Notify me of followup comments via e-mail. Unfortunately, no. However, there is a significant difference between this scenario. In simple words, the destination recipient is not aware of a scenario in which the SPF result is Fail, and they are not aware of the fact that the E-mail message could be a spoofed E-mail. This tag allows plug-ins or applications to run in an HTML window. The organization publishes an SPF record (implemented as TXT record) that includes information about the IP address of the mail servers, which are authorized to send an E-mail message on behalf of the particular domain name. We will review how to enable the option of SPF record: hard fail at the end of the article. We recommend the value -all. For example, Exchange Online Protection plus another email system. In other words, using SPF can improve our E-mail reputation. SPF records in Office 365 are DNS records that help authenticate Office 365 based emails so organizations can operate with higher levels of trust and prevent spoofing. This phase is described as learning mode or inspection mode because the purpose of this step has been just to identify an event of a Spoof mail attack in which the hostile element uses an E-mail address that includes our domain name + Log this information.
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