Sender Policy Framework (SPF) allows email administrators to reduce sender-address forgery (spoofing) by specifying which are allowed to send email for a domain. This list is known as the SPF record. 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. In the next two articles (Implementing SPF Fail policy using Exchange Online rule (dealing with Spoof E-mail attack) | Phase 1 learning mode | Part 2#3 and Implementing SPF Fail policy using Exchange Online rule (dealing with Spoof E-mail attack) | Phase 2 production | part 3#3), we will review in details the implementation of SPF fail policy by using an Exchange Online rule. is required for every domain and subdomain to prevent attackers from sending email claiming to be from non-existent subdomains. Misconception 3: In Office 365 and Exchange Online based environment the SPF protection mechanism is automatically activated. This option enables us to activate an EOP filter, which will mark incoming E-mail message that has the value of SFP =Fail as spam mail (by setting a high SCL value). From my experience, the phase is fascinating because after we activate the monitor process, we will usually find an absorbing finding of: Based on this information, we will be able to understand the real scope of the problem, the main characters of this attack and so on. This conception is half true. Include the following domain name: spf.protection.outlook.com. This is the scenario in which we get a clear answer regarding the result from the SPF sender verification test the SPF test fail! We can say that the SPF mechanism is neutral to the results his main responsibility is to execute the SPF sender verification test and to add the results to the E-mail message header. The SPF sender verification can mark a particular E-mail message with a value to SPF = none or SPF = Fail. 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. When this setting is enabled, any message that hard fails a conditional Sender ID check is marked as spam. Did you know you can try the features in Microsoft 365 Defender for Office 365 Plan 2 for free? This type of scenario, there is a high chance that we are experiencing a Spoof mail attack! Hope this helps. If you provided a sample message header, we might be able to tell you more. This will avoid the rejections taking place by some email servers with strict settings for their SPF checks. 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. You can also subscribe without commenting. Office 365 supports only one SPF record (a TXT record that defines SPF) for your domain. By rewriting the SMTP MAIL FROM, SRS can ensure that the forwarded message passes SPF at the next destination. What happens to the message is determined by the Test mode (TestModeAction) value: The following Increase spam score ASF settings result in an increase in spam score and therefore a higher chance of getting marked as spam with a spam confidence level (SCL) of 5 or 6, which corresponds to a Spam filter verdict and the corresponding action in anti-spam policies. Add a new Record Select Type: TXT Name/Host: @ Content/Value: v=spf1 include:spf.protection.outlook.com -all (or copy paste it from Microsoft 365 ( step 4 )) Click SaveContinue at Step 8, If you already have an SPF record, then you will need to edit it. Take a look at the basic syntax for an SPF rule: For example, let's say the following SPF rule exists for contoso.com: v=spf1 . 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. To avoid this, you can create separate records for each subdomain. Off: The ASF setting is disabled. 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. Scenario 1. My opinion that blocking or rejecting such E-mail messages is too risky because, we cannot enforce other organizations to use SPF, although using SPF is recommended and help to protect the identity and the reputation of a particular domain. Sender Policy Framework, or SPF, is an email authentication technique that helps protect email senders and recipients from spam, phishing and spoofing. Next, see Use DMARC to validate email in Microsoft 365. Solved Microsoft Office 365 Email Anti-Spam. SPF is configured by adding a specially formatted TXT record to the DNS zone for the domain. You need all three in a valid SPF TXT record. While there was disruption at first, it gradually declined. This is no longer required. The SPF information identifies authorized outbound email servers. What does SPF email authentication actually do? Each SPF TXT record contains three parts: the declaration that it's an SPF TXT record, the IP addresses that are allowed to send mail from your domain and the external domains that can send on your domain's behalf, and an enforcement rule. Nearly all large email services implement traditional SPF, DKIM, and DMARC checks. What is the conclusion such as scenario, and should we react to such E-mail message? Q2: Why does the hostile element use our organizational identity? As mentioned, the SPF sender verification test just stamp the E-mail message with information about the SPF test result. DKIM is the second step in protecting your mail domain against spoofing and phishing attempts. Now that Enhanced Filtering for Connectors is available, we no longer recommended turning off anti-spoofing protection when your email is routed through another service before EOP. Also, if you're using DMARC with p=quarantine or p=reject, then you can use ~all. Login at admin.microsoft.com Navigate to your domain - Expand Settings and select Domains - Select your custom Domain (not the <companyname>.onmicrosoft.com domain Lookup the SPF Record Click on the DNS Records tab. Edit Default > connection filtering > IP Allow list. For more information, see Advanced Spam Filter (ASF) settings in EOP. SPF record types were deprecated by the Internet Engineering Task Force (IETF) in 2014. If you don't have a deployment that is fully hosted in Microsoft 365, or you want more information about how SPF works or how to troubleshoot SPF for Microsoft 365, keep reading. 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. There is no right answer or a definite answer that will instruct us what to do in such scenarios. Enabling one or more of the ASF settings is an aggressive approach to spam filtering. If an SPF TXT record exists, instead of adding a new record, you need to update the existing record. Summary: This article describes how Microsoft 365 uses the Sender Policy Framework (SPF) TXT record in DNS to ensure that destination email systems trust messages sent from your custom domain. A9: The answer depends on the particular mail server or the mail security gateway that you are using. We don't recommend that you use this qualifier in your live deployment. 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. For instructions, see Gather the information you need to create Office 365 DNS records. For example, at the time of this writing, Salesforce.com contains 5 include statements in its record: To avoid the error, you can implement a policy where anyone sending bulk email, for example, has to use a subdomain specifically for this purpose. Indicates soft fail. Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. For example: Once you've formulated your SPF TXT record, follow the steps in Set up SPF in Microsoft 365 to help prevent spoofing to add it to your domain. Edit Default > advanced optioins > Mark as Spam > SPF record: hard fail: Off. If you're using IPv6 IP addresses, replace ip4 with ip6 in the examples in this article. 2. We will review how to enable the option of SPF record: hard fail at the end of the article. More info about Internet Explorer and Microsoft Edge, Microsoft Defender for Office 365 plan 1 and plan 2, Set up SPF in Microsoft 365 to help prevent spoofing, Troubleshooting: Best practices for SPF in Microsoft 365, Example: SPF TXT record for multiple outbound on-premises mail servers and Microsoft 365, Use DKIM to validate outbound email sent from your custom domain in Microsoft 365, Use DMARC to validate email in Microsoft 365, Create DNS records at any DNS hosting provider for Microsoft 365. The answer is that as always; we need to avoid being too cautious vs. being too permissive. This is the default value, and we recommend that you don't change it. 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. Sender Policy Framework or SPF decides if a sender is authorized to send emails for any domain. If the receiving server finds out that the message comes from a server other than the Office 365 messaging servers listed in the SPF record, the receiving mail server can choose to reject the message as spam. 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. Another distinct advantage of using Exchange Online is the part which enables us to select a very specific response (action), that will suit our needs such as Perpend the E-mail message subject, Send warning E-mail, send the Spoof mail to quarantine, generate the incident report and so on. Exchange Online (EOP), include spam filter policy, which contains many security settings that are disabled by default and can be activated manually based on the particular mail security policy that the organization wants to implement. No. Keep in mind, that SPF has a maximum of 10 DNS lookups. Creating multiple records causes a round robin situation and SPF will fail. The following Mark as spam ASF settings set the SCL of detected messages to 6, which corresponds to a Spam filter verdict and the corresponding action in anti-spam policies. A good option could be, implementing the required policy in two phases-. Implement the SPF Fail policy using a two-phase procedure the learning/inspection phase and the production phase. In this category, we can put every event in which a legitimate E-mail message includes the value of SPF = Fail. Periodic quarantine notifications from spam and high confidence spam filter verdicts. The receiving server may also respond with a non-delivery report (NDR) that contains an error similar to these: Some SPF TXT records for third-party domains direct the receiving server to perform a large number of DNS lookups. This option described as . Sharing best practices for building any app with .NET. But it doesnt verify or list the complete record. Otherwise, use -all. How to enforce SPF fail policy in Office 365 (Exchange Online) based environment, The main two purposes of using SPF mechanism, Scenario 1: Improve our E-mail reputation (domain name), Scenario 2: Incoming mail | Protect our users from Spoof mail attack, The popular misconception relating to SPF standard. It can take a couple of minutes up to 24 hours before the change is applied. For example, suppose the user at woodgrovebank.com has set up a forwarding rule to send all email to an outlook.com account: The message originally passes the SPF check at woodgrovebank.com but it fails the SPF check at outlook.com because IP #25 isn't in contoso.com's SPF TXT record. Can we say that we should automatically block E-mail message which their organization doesnt support the use of SPF? Even in a scenario in which the mail infrastructure of the other side support SPF, in case that the SPF verification test marked as Fail, we cannot be sure that the spoofed E-mail will be blocked. 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. By analyzing the information thats collected, we can achieve the following objectives: 1. i check headers and see that spf failed. Depending on the property, ASF detections will either mark the message as Spam or High confidence spam. This conception is partially correct because of two reasons: Misconception 2: SPF mechanism was built for identifying an event of incoming mail, in which the sender Spoof his identity, and as a response, react to this event and block the specific E-mail message. An SPF TXT record is a DNS record that helps prevent spoofing and phishing by verifying the domain name from which email messages are sent. The SPF TXT record for Office 365 will be made in external DNS for any custom domains or subdomains. 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. You will also need to watch out for the condition where you SPF record contains more than 10 DNS lookups, and take action to fix it when it happens. 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. If you've already set up mail for Office 365, then you have already included Microsoft's messaging servers in DNS as an SPF TXT record. SPF enables receiving mail servers to authenticate whether an email message was sent from an authorized mail server - but only when the domain owner's SPF record is valid. We can certainly give some hints based on the header information and such, but it might as well be something at the backend (like the changes which caused the previous "incident"). Make sure that you include all mail systems in your SPF record, otherwise, mail sent from these systems will be listed as spam messages. You add an SPF TXT record that lists the Office 365 messaging servers as legitimate mail servers for your domain. However, anti-phishing protection works much better to detect these other types of phishing methods. If you do not use any external third-party email services and route all your emails via Office 365, your SPF record will have the following syntax: v=spf1 include:spf.protection.outlook.com -all. Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type. Join the movement and receive our weekly Tech related newsletter. Test: ASF adds the corresponding X-header field to the message. Note: MailRoute will automatically recognize that you are using Office 365 for your outbound service, so you do not need to enter an outbound mailserver in the MailRoute Control Panel. Office 365 supports only one SPF record (a TXT record that defines SPF) for your domain. Q9: So how can I activate the option to capture events of an E-mail message that have the value of SPF = Fail? See Report messages and files to Microsoft. In this scenario, we can choose from a variety of possible reactions.. Given that the SPF record is configured correctly, and given that the SPF record includes information about all of our organizations mail server entities, there is no reason for a scenario in which a sender E-mail address which includes our domain name will mark by the SPF sender verification test as Fail. This setting combines an SPF check with a Sender ID check to help protect against message headers that contain forged senders. This change should reduce the risk of SharePoint Online notification messages ending up in the Junk Email folder. is the domain of the third-party email system. SPF helps validate outbound email sent from your custom domain (is coming from who it says it is). 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) A8: The responsibility of the SPF mechanism is to stamp the E-mail message with the SPF sender verification test results.