In case the mail server IP address that sends the E-mail on behalf of the sender, doesnt appear as authorized IP address in the SPF record, SPF sender verification test result is Fail. It can take a couple of minutes up to 24 hours before the change is applied. In Office 365 based environment (Exchange Online and EOP) beside the option of using Exchange rule, we can use an additional option the spam filter policy. You need all three in a valid SPF TXT record. A1: A Spoof mail attack implemented when a hostile element, uses a seemingly legitimate sender identity. 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. You can also specify IP address ranges using CIDR notation, for example ip4:192.168.0.1/26. Office 365 supports only one SPF record (a TXT record that defines SPF) for your domain. SPF sender verification test fail | External sender identity. 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. Below is an example of adding the office 365 SPF along with onprem in your public DNS server. You do not need to make any changes immediately, but if you receive the "too many lookups" error, modify your SPF TXT record as described in Set up SPF in Microsoft 365 to help prevent spoofing. This setting combines an SPF check with a Sender ID check to help protect against message headers that contain forged senders. We reviewed the need for completing the missing part of our SPF implementation, in which we need to capture an event of SPF sender verification test in which the result is fail and, especially, in a scenario in which the sender E-mail address includes our domain name (most likely certainly a sign that this is a Spoof mail attack). If you're not sure that you have the complete list of IP addresses, then you should use the ~all (soft fail) qualifier. For instructions, see Gather the information you need to create Office 365 DNS records. The condition part will activate the Exchange rule when the combination of the following two events will occur: In phase 1 (the learning mode), we will execute the following sequence of actions: This phase is implemented after we are familiar with the different scenarios of Spoof mail attacks. Q5: Where is the information about the result from the SPF sender verification test stored? If you have any questions, just drop a comment below. Customers on US DC (US1, US2, US3, US4 . In all Microsoft 365 organizations, the Advanced Spam Filter (ASF) settings in anti-spam policies in EOP allow admins to mark messages as spam based on specific message properties. by We recommend that you disable this feature as it provides almost no additional benefit for detecting spam or phishing message, and would instead generate mostly false positives. This type of mail threat appears in two flavors: In this section, I would like to review a couple of popular misconceptions that relate to the SPF standard. To get started, see Use DKIM to validate outbound email sent from your custom domain in Microsoft 365. A soft fail would look like this: v=spf1 ip4 192.xx.xx.xx ~all This is the scenario in which we get a clear answer regarding the result from the SPF sender verification test the SPF test fail! 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. A9: The answer depends on the particular mail server or the mail security gateway that you are using. Some online tools will even count and display these lookups for you. 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. 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. @tsulafirstly, this mostly depends on the spam filtering policy you have configured. Include the following domain name: spf.protection.outlook.com. 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. An SPF record is a list of authorized sending hosts for the domain listed in the return path of an email. In case we decide to activate this option, the result is that each of the incoming E-mails accepted by our Office 365 mail server (EOP), and that include SPF sender verification results of SPF = Fail, will automatically be marked as spam mail. More info about Internet Explorer and Microsoft Edge, Microsoft Defender for Office 365 plan 1 and plan 2, You don't know all sources for your email, Advanced Spam Filter (ASF) settings in EOP. It doesn't have the support of Microsoft Outlook and Office 365, though. So before we can create the SPF record we first need to know which systems are sending mail on behalf of your domain, besides Office 365. Can we say that we should automatically block E-mail message which their organization doesnt support the use of SPF? 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"). If the sender isn't permitted to do so, that is, if the email fails the SPF check on the receiving server, the spam policy configured on that server determines what to do with the message. This is where we use the learning/inspection mode phase and use it as a radar that helps us to locate anomalies and other infrastructure security issues. When Microsoft enabled this feature in 2018, some false positives happened (good messages were marked as bad). For tips on how to avoid this, see Troubleshooting: Best practices for SPF in Microsoft 365. These scripting languages are used in email messages to cause specific actions to automatically occur. Scenario 1 the sender uses an E-mail address that includes a domain name of a well-known organization. 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. If you have a hybrid environment with Office 365 and Exchange on-premises. If you're using IPv6 IP addresses, replace ip4 with ip6 in the examples in this article. See Report messages and files to Microsoft. Your support helps running this website and I genuinely appreciate it. A wildcard SPF record (*.) How to deal with a Spoof mail attack using SPF policy in Exchange-based environment, Exchange Online | Using the option of the spam filter policy, How to configure Exchange Online spam filter policy to mark SPF fail as spam, Implementing SPF Fail policy using Exchange Online rule (dealing with Spoof E-mail attack) | Phase 1 learning mode, Implementing SPF Fail policy using Exchange Online rule (dealing with Spoof E-mail attack) | Phase 2 production, Implementing SPF Fail policy using Exchange Online rule (dealing with Spoof E-mail attack) | Phase 1 learning mode | Part 2#3, Implementing SPF Fail policy using Exchange Online rule (dealing with Spoof E-mail attack) | Phase 2 production | part 3#3), Submit a request for removing your mail server IP from Office 365 black list, My E-mail appears as spam | Troubleshooting Mail server | Part 14#17, Detect spoof E-mail and add disclaimer using Exchange Online rule |Part 6#12, Create unlimited Client Secret in Azure AD, Configure Certificate Based Authentication to run automated PowerShell scripts, Implementing SPF Fail policy using Exchange Online rule (dealing with Spoof E-mail attack) | Introduction (this article), Case 1 a scenario in which the hostile element uses the spoofed identity of a, Case 2 a scenario in which the hostile element uses a spoofed identity of. 04:08 AM Q10: Why our mail server doesnt automatically block incoming E-mail that has the value of SPF = Fail? A typical SPF TXT record for Microsoft 365 has the following syntax: v=spf1 is required. The defense action that we will choose to implement in our particular scenario is a process in which E-mail message that identified as Spoof mail, will not be sent to the original destination recipient.. I always try to make my reviews, articles and how-to's, unbiased, complete and based on my own expierence. If you have anti-spoofing enabled and the SPF record: hard fail ( MarkAsSpamSpfRecordHardFail) turned on, you will probably get more false positives. In case that your organization experiences a scenario in which your mail server IP address, In the current article and the next article: My E-mail appears as spam | Troubleshooting, In the current article, we will review how to deal with Spoof mail by creating, Your email address will not be published. Attackers will adapt to use other techniques (for example, compromised accounts or accounts in free email services). 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. All SPF TXT records end with this value. Share. This is no longer required. For a list of domain names you should include for Microsoft 365, see External DNS records required for SPF. Getting Started with PDQ Deploy & Inventory, Automatically assign licenses in Office 365, Match all domain name records (A and AAAA), Match all listed MX records. Add a predefined warning message, to the E-mail message subject. This is the default value, and we recommend that you don't change it. This allows you to copy the TXT value and also check if your domain already has an SPF record (it will be listed as Invalid Entry). Step 2: Set up SPF for your domain. A8: The responsibility of the SPF mechanism is to stamp the E-mail message with the SPF sender verification test results. SPF is configured by adding a specially formatted TXT record to the DNS zone for the domain. You can identify messages that were filtered by ASF by: The following sections describe the ASF settings and options that are available in anti-spam policies in the Microsoft 365 Defender portal, and in Exchange Online PowerShell or standalone EOP PowerShell (New-HostedContentFilterPolicy and Set-HostedContentFilterPolicy).
