| V-259642 | High | Exchange internal Send connectors must require encryption. | The Simple Mail Transfer Protocol (SMTP) connector is used by Exchange to send and receive messages from server to server. Several controls work together to provide security between internal... |
| V-259640 | High | Exchange must provide redundancy. | Denial of Service (DoS) is a condition when a resource is not available for legitimate users. When this occurs, the organization either cannot accomplish its mission or must operate at degraded... |
| V-259641 | High | Exchange internal Receive connectors must require encryption. | The Simple Mail Transfer Protocol (SMTP) Receive connector is used by Exchange to send and receive messages from server to server using SMTP protocol. This setting controls the encryption strength... |
| V-259599 | Medium | Exchange receive connector maximum hop count must be 60. | Email system availability depends in part on best practice strategies for setting tuning configurations. This setting controls the maximum number of hops (email servers traversed) a message may... |
| V-259598 | Medium | Exchange Outbound Connection limit per Domain Count must be controlled. | Email system availability depends in part on best practice strategies for setting tuning configurations. This configuration controls the maximum number of simultaneous outbound connections from a... |
| V-259622 | Medium | Exchange internal Receive connectors must not allow anonymous connections. | This control is used to limit the servers that may use this server as a relay. If a Simple Mail Transport Protocol (SMTP) sender does not have a direct connection to the internet (for example, an... |
| V-259629 | Medium | Exchange Sender Identification Framework must be enabled. | Email is only as secure as the recipient. When the recipient is an email server accepting inbound messages, authenticating the sender enables the receiver to better assess message quality and to... |
| V-259591 | Medium | Exchange Send Fatal Errors to Microsoft must be disabled. | It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked... |
| V-259590 | Medium | Exchange must not send customer experience reports to Microsoft. | It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked... |
| V-259593 | Medium | Exchange internet-facing send connectors must specify a Smart Host. | When identifying a "Smart Host" for the email environment, a logical send connector is the preferred method.
A Smart Host acts as an internet-facing concentrator for other email servers.... |
| V-259592 | Medium | Exchange queue database must reside on a dedicated partition. | In the same way that added security layers can provide a cumulative positive effect on security posture, multiple applications can provide a cumulative negative effect. A vulnerability and... |
| V-259595 | Medium | Exchange internet-facing receive connectors must offer Transport Layer Security (TLS) before using basic authentication. | Sending unencrypted email over the internet increases the risk that messages can be intercepted or altered. TLS is designed to protect confidentiality and data integrity by encrypting email... |
| V-259594 | Medium | Exchange internal send connectors must use domain security (mutual authentication Transport Layer Security). | The Simple Mail Transfer Protocol (SMTP) connector is used by Exchange to send and receive messages from server to server. Several controls work together to provide security between internal... |
| V-259597 | Medium | Exchange Outbound Connection Timeout must be 10 minutes or less. | Email system availability depends in part on best practice strategies for setting tuning configurations. This configuration controls the number of idle minutes before the connection is dropped. It... |
| V-259596 | Medium | More than one Edge server must be deployed. | To ensure hostile insiders are unable to easily commit DoS attacks and reduce the effectiveness of mail flow throughout the environment, a second Edge server is deployed to allow for multiple... |
| V-259605 | Medium | Exchange receive connectors must control the number of recipients chunked on a single message. | Email system availability depends in part on best practice strategies for setting tuning configurations. For message size restrictions, multiple places exist to set or override inbound or outbound... |
| V-259604 | Medium | Exchange receive connectors must be clearly named. | For receive connectors, unclear naming as to direction and purpose increases risk that messages may not flow as intended, troubleshooting efforts may be impaired, or incorrect assumptions may be... |
| V-259607 | Medium | Exchange Message size restrictions must be controlled on receive connectors. | Email system availability depends in part on best practices strategies for setting tuning configurations. For message size restrictions, multiple places exist to set or override inbound or... |
| V-259606 | Medium | The Exchange internet receive connector connections count must be set to default. | Email system availability depends in part on best practice strategies for setting tuning configurations. This configuration controls the maximum number of simultaneous inbound connections allowed... |
| V-259601 | Medium | Exchange send connector connections count must be limited. | This setting controls the maximum number of simultaneous outbound connections allowed for a given SMTP Connector and can be used to throttle the SMTP service if resource constraints warrant it. If... |
| V-259600 | Medium | Exchange receive connectors must control the number of recipients per message. | Email system availability depends in part on best practice strategies for setting tuning configurations.
This configuration controls the maximum number of recipients who will receive a copy of a... |
| V-259603 | Medium | Exchange send connectors delivery retries must be controlled. | This setting controls the rate at which delivery attempts from the home domain are retried and user notifications are issued and notes the expiration time when the message will be discarded.
If... |
| V-259602 | Medium | Exchange message size restrictions must be controlled on Send connectors. | Email system availability depends in part on best practice strategies for setting tuning configurations. For message size restrictions, multiple places exist to set or override inbound or outbound... |
| V-259627 | Medium | Exchange must have anti-spam filtering enabled. | Originators of spam messages are constantly changing their techniques to defeat spam countermeasures; therefore, spam software must be constantly updated to address the changing threat. Spam... |
| V-259626 | Medium | Exchange must have anti-spam filtering installed. | Originators of spam messages are constantly changing their techniques to defeat spam countermeasures; therefore, spam software must be constantly updated to address the changing threat. Spam... |
| V-259625 | Medium | The Exchange Simple Mail Transfer Protocol (SMTP) Sender filter must be enabled. | Email system availability depends in part on best practices strategies for setting tuning configurations. Careful tuning reduces the risk that system or network congestion will contribute to... |
| V-259624 | Medium | The Exchange Simple Mail Transfer Protocol (SMTP) IP Allow List Connection filter must be enabled. | Email system availability depends in part on best practice strategies for setting tuning configurations. Careful tuning reduces the risk that system or network congestion will contribute to... |
| V-259609 | Medium | Exchange messages with a blank sender field must be rejected. | By performing filtering at the perimeter, up to 90 percent of spam, malware, and other undesirable messages are eliminated from the message stream rather than admitting them into the mail server... |
| V-259608 | Medium | Active hyperlinks in messages from non .mil domains must be rendered unclickable. | Active hyperlinks within an email are susceptible to attacks of malicious software or malware. The hyperlink could lead to a malware infection or redirect the website to another fraudulent website... |
| V-259621 | Medium | The Exchange tarpitting interval must be set. | Tarpitting is the practice of artificially delaying server responses for specific Simple Mail Transfer Protocol (SMTP) communication patterns that indicate high volumes of spam or other unwelcome... |
| V-259620 | Medium | The Exchange Recipient filter must be enabled. | Email system availability depends in part on best practice strategies for setting tuning configurations. Careful tuning reduces the risk that system or network congestion will contribute to... |
| V-259577 | Medium | SchUseStrongCrypto must be enabled. | Exchange Server 2019 is configured by default with TLS 1.2. However, SchUseStrongCrypto is not set by default and must be configured to meet the TLS requirement. The strong cryptography... |
| V-259623 | Medium | Exchange Simple Mail Transfer Protocol (SMTP) IP Allow List entries must be empty. | Email system availability depends in part on best practice strategies for setting tuning configurations. Careful tuning reduces the risk that system or network congestion will contribute to... |
| V-259618 | Medium | The Exchange Block List service provider must be identified. | Block List filtering is a sanitization process performed on email messages prior to their arrival at the destination mailbox. By performing this process at the email perimeter, threats can be... |
| V-259579 | Medium | Exchange must have accepted domains configured. | Exchange may be configured to accept email for multiple domain names. This setting identifies the domains for which the server will accept mail. This check verifies the email server is not... |
| V-259578 | Medium | Exchange servers must use approved DOD certificates. | To mitigate the risk of unauthorized access to sensitive information by entities that have been issued certificates by DOD-approved PKIs, all DOD systems (e.g., networks, web servers, and web... |
| V-259580 | Medium | Exchange external Receive connectors must be domain secure-enabled. | The Simple Mail Transfer Protocol (SMTP) connector is used by Exchange to send and receive messages from server to server. Several controls work together to provide security between internal... |
| V-259588 | Medium | Exchange audit data must be on separate partitions. | Log files help establish a history of activities and can be useful in detecting attack attempts or determining tuning adjustments to improve availability. Audit log content must always be... |
| V-259589 | Medium | Exchange local machine policy must require signed scripts. | Scripts often provide a way for attackers to infiltrate a system, especially scripts downloaded from untrusted locations. By setting machine policy to prevent unauthorized script executions,... |
| V-259617 | Medium | The Exchange Spam Evaluation filter must be enabled. | By performing filtering at the perimeter, up to 90 percent of spam, malware, and other undesirable messages may be eliminated from the transport message stream, preventing their entry into the... |
| V-259586 | Medium | Exchange audit data must be protected against unauthorized access for modification. | Log files help establish a history of activities and can be useful in detecting attack attempts or determining tuning adjustments to improve availability. Audit log content must always be... |
| V-259587 | Medium | Exchange audit data must be protected against unauthorized access for deletion. | Log files help establish a history of activities and can be useful in detecting attack attempts or determining tuning adjustments to improve availability. Audit log content must always be... |
| V-259643 | Medium | Exchange must render hyperlinks from email sources from non-.mil domains as unclickable. | Active hyperlinks within an email are susceptible to attacks of malicious software or malware. The hyperlink could lead to a malware infection or redirect the website to another fraudulent website... |
| V-259585 | Medium | Exchange audit data must be protected against unauthorized access (read access). | Log files help establish a history of activities and can be useful in detecting attack attempts or determining tuning adjustments to improve availability. Audit log content must always be... |
| V-259582 | Medium | Exchange connectivity logging must be enabled. | A connectivity log is a record of the SMTP connection activity of the outbound message delivery queues to the destination mailbox server, smart host, or domain. Connectivity logging is available... |
| V-259639 | Medium | Exchange internal Send connectors must use an authentication level. | The Simple Mail Transfer Protocol (SMTP) connector is used by Exchange to send and receive messages from server to server. Several controls work together to provide security between internal... |
| V-259614 | Medium | The Exchange Sender Reputation filter must be enabled. | By performing filtering at the perimeter, up to 90 percent of spam, malware, and other undesirable messages are eliminated from the message stream rather than admitting them into the mail server... |
| V-259581 | Medium | The Exchange email diagnostic log level must be set to the lowest level. | Log files help establish a history of activities and can be useful in detecting attack attempts or determining tuning adjustments to improve availability. Diagnostic logging, however,... |
| V-259634 | Medium | The Exchange local machine policy must require signed scripts. | Scripts, especially those downloaded from untrusted locations, often provide a way for attackers to infiltrate a system. By setting machine policy to prevent unauthorized script executions,... |
| V-259635 | Medium | Exchange services must be documented, and unnecessary services must be removed or disabled. | Unneeded but running services offer attackers an enhanced attack profile, and attackers are constantly watching to discover open ports with running services. By analyzing and disabling unneeded... |
| V-259636 | Medium | The Exchange Edge server must point to a trusted list of DNS servers for external and internal resolution. | To mitigate the risk of possible erroneous queries that may have been coopted by bad actors, the Exchange Edge server must use DNS servers that utilize DNSSEC to resolve external hosts and... |
| V-259637 | Medium | Exchange software must be installed on a separate partition from the OS. | In the same way that added security layers can provide a cumulative positive effect on security posture, multiple applications can provide a cumulative negative effect. A vulnerability and... |
| V-259630 | Medium | Exchange must limit the Receive connector timeout. | Email system availability depends in part on best practices strategies for setting tuning. This configuration controls the number of idle minutes before the connection is dropped. It works in... |
| V-259631 | Medium | Role-Based Access Control must be defined for privileged and nonprivileged users. | Role Based Access Control (RBAC) is the permissions model used in Microsoft Exchange Server 2013, 2016, and 2019. With RBAC, there is no need to modify and manage access control lists (ACLs),... |
| V-259632 | Medium | The Exchange application directory must be protected from unauthorized access. | Default product installations may provide more generous access permissions than are necessary to run the application. By examining and tailoring access permissions to provide the least amount of... |
| V-259633 | Medium | The Exchange software baseline copy must exist. | Exchange software, as with other application software installed on a host system, must be included in a system baseline record and periodically reviewed; otherwise, unauthorized changes to the... |
| V-259612 | Medium | The Exchange sender filter must block unaccepted domains. | Spam origination sites and other sources of suspected email-borne malware have the ability to corrupt, compromise, or otherwise limit availability of email servers. Limiting exposure to unfiltered... |
| V-259610 | Medium | Exchange messages with a blank sender field must be filtered. | By performing filtering at the perimeter, up to 90 percent of spam, malware, and other undesirable messages are eliminated from the message stream rather than admitting them into the mail server... |
| V-259613 | Medium | Exchange nonexistent recipients must not be blocked. | Spam originators, in an effort to refine mailing lists, sometimes use a technique where they first create fictitious names and then monitor rejected emails for nonexistent recipients. Those not... |
| V-259628 | Medium | Exchange must have anti-spam filtering configured. | Originators of spam messages are constantly changing their techniques to defeat spam countermeasures; therefore, spam software must be constantly updated to address the changing threat. A manual... |
| V-259584 | Medium | Exchange queue monitoring must be configured with threshold and action. | Monitors are automated "process watchers" that respond to performance changes and can be useful in detecting outages and alerting administrators where attention is needed. Exchange has built-in... |
| V-259619 | Medium | Exchange messages with a malformed From address must be rejected. | Sender Identification (SID) is an email anti-spam sanitization process. Sender ID uses DNS MX record lookups to verify the Simple Mail Transfer Protocol (SMTP) sending server is authorized to send... |
| V-259611 | Medium | Exchange filtered messages must be archived. | By performing filtering at the perimeter, up to 90 percent of spam, malware, and other undesirable messages are eliminated from the message stream rather than admitting them into the mail server... |
| V-259644 | Medium | Exchange must have the most current, approved Cumulative Update (CU) installed. | The organization (including any contractor to the organization) must promptly install security-relevant software updates (e.g., patches, service packs, CUs, hot fixes). Flaws discovered during... |
| V-259616 | Medium | Exchange Attachment filtering must remove undesirable attachments by file type. | By performing filtering at the perimeter, up to 90 percent of spam, malware, and other undesirable messages are eliminated from the message stream rather than admitting them into the mail server... |
| V-259615 | Medium | The Exchange Sender Reputation filter must identify the spam block level. | By performing filtering at the perimeter, up to 90 percent of spam, malware, and other undesirable messages are eliminated from the message stream rather than admitting them into the mail server... |
| V-259638 | Medium | The Exchange SMTP automated banner response must not reveal server details. | Automated connection responses occur as a result of FTP or Telnet connections when connecting to those services. They report a successful connection by greeting the connecting client and stating... |
| V-259583 | Medium | Exchange message tracking logging must be enabled. | A message tracking log provides a detailed log of all message activity as messages are transferred to and from a computer running Exchange.
If events are not recorded, it may be difficult or... |
