transportConfig

Transport Settings. Organization-wide mail flow and transport configuration settings. The transportConfig singleton lives under /exchange/v1.0/transportConfig in the Mail flow category.

Fact	Value
Path	`/exchange/v1.0/transportConfig`
Category	Mail flow
Tier	Tier 9, Hybrid and organization
Read role	`OrganizationConfig.Read.All` (Community)
Write role	`OrganizationConfig.ReadWrite.All` (Enterprise)
Backing cmdlets	Get-TransportConfig, Set-TransportConfig

Routes

Method	Path	Synopsis	Role	Plan
GET	`/exchange/v1.0/transportConfig`	Read the tenant’s transportConfig singleton.	`OrganizationConfig.Read`	Community
PATCH	`/exchange/v1.0/transportConfig`	Partial update of the transportConfig singleton via Set-TransportConfig. Body keys map 1:1 to cmdlet params (camelCased). Returns 200 + the post-Set entity.	`OrganizationConfig.ReadWrite`	Enterprise

GET /exchange/v1.0/transportConfig

Read the tenant’s transportConfig singleton.

Backing cmdlet: Get-TransportConfig. Role: OrganizationConfig.Read (Community).

Get the organization transport configuration

Returns the tenant-wide transport (mail flow) configuration singleton, including DSN behavior, message size limits, journaling, transport-rule limits, and reply-all storm protection. Backed by the Get-TransportConfig cmdlet.

GET /exchange/v1.0/transportConfig HTTP/1.1
Authorization: Bearer {token}

HTTP/1.1 200 OK

{
  "@odata.context": "http://localhost:5043/exchange/v1.0/$metadata#transportConfig",
  "Id": "Transport Settings",
  "Name": "Transport Settings",
  "Identity": "Transport Settings",
  "DistinguishedName": "CN=Transport Settings,CN=Configuration,CN=contoso.onmicrosoft.com,CN=ConfigurationUnits,DC=EURPR01A017,DC=PROD,DC=OUTLOOK,DC=COM",
  "Guid": "b68529c3-2904-4074-ba5e-61472e14e722",
  "ExchangeObjectId": "0693a0a1-31cc-48e6-a781-78e634c3401f",
  "MaxRecipientEnvelopeLimit": 0,
  "MaxReceiveSize": 0,
  "MaxSendSize": 0,
  "MaxRetriesForLocalSiteShadow": 0,
  "MaxRetriesForRemoteSiteShadow": 0,
  "ShadowMessageAutoDiscardInterval": null,
  "ShadowHeartbeatRetryCount": null,
  "JournalingReportNdrTo": 0,
  "ConvertReportToMessage": null,
  "ExternalDsnSendHtml": true,
  "InternalDsnSendHtml": true,
  "ExternalDsnLanguageDetectionEnabled": "True",
  "InternalDsnLanguageDetectionEnabled": "True",
  "ExternalDsnDefaultLanguage": null,
  "InternalDsnDefaultLanguage": null,
  "ExternalDelayDsnEnabled": "True",
  "InternalDelayDsnEnabled": "True",
  "ExternalDsnMaxMessageAttachSize": "10 MB (10,485,760 bytes)",
  "InternalDsnMaxMessageAttachSize": "10 MB (10,485,760 bytes)",
  "OpenDomainRoutingEnabled": false,
  "DSNConversionMode": false,
  "VoicemailJournalingEnabled": true,
  "InternalSMTPServers": [],
  "GenerateCopyOfDSNFor": [],
  "JournalingReportNdrToAddress": null,
  "Rfc2231EncodingEnabled": false,
  "SmtpClientAuthenticationDisabled": true,
  "AddressRewriteEnabled": false,
  "AcceptedDomain": [],
  "HeaderPromotionModeSetting": "NoCreate",
  "Rfc5965PinEnabled": null,
  "RejectMessageOnX400OriginatorMismatch": null,
  "SafetyNetHoldTime": "7.00:00:00",
  "ReplyAllStormBlockDurationHours": "6",
  "ReplyAllStormDetectionMinimumReplies": "10",
  "ReplyAllStormDetectionMinimumRecipients": "2500",
  "ReplyAllStormProtectionEnabled": true,
  "OrganizationalUnitRoot": "contoso.onmicrosoft.com",
  "OrganizationId": "EURPR01A017.PROD.OUTLOOK.COM/Microsoft Exchange Hosted Organizations/contoso.onmicrosoft.com - EURPR01A017.PROD.OUTLOOK.COM/ConfigurationUnits/contoso.onmicrosoft.com/Configuration",
  "ExchangeVersion": "0.1 (8.0.535.0)",
  "ObjectCategory": "EURPR01A017.PROD.OUTLOOK.COM/Configuration/Schema/ms-Exch-Transport-Settings",
  "ObjectClass": [
    "top",
    "container",
    "msExchTransportSettings"
  ],
  "OriginatingServer": "VI1PR01A17DC001.EURPR01A017.PROD.OUTLOOK.COM",
  "ObjectState": "Unchanged",
  "IsValid": true,
  "WhenCreated": "2026-03-30T17:01:11+03:00",
  "WhenChanged": "2026-03-30T17:01:18+03:00",
  "WhenCreatedUTC": "2026-03-30T14:01:11Z",
  "WhenChangedUTC": "2026-03-30T14:01:18Z",
  "AddressBookPolicyRoutingEnabled": false,
  "AdminDisplayName": "",
  "AgentGeneratedMessageLoopDetectionInSmtpEnabled": true,
  "AgentGeneratedMessageLoopDetectionInSubmissionEnabled": true,
  "AllowLegacyTLSClients": false,
  "AnonymousSenderToRecipientRatePerHour": 1800,
  "AttributionRejectBeforeMServRequest": false,
  "AttributionRejectConsumerMessages": false,
  "ClearCategories": true,
  "ConvertDisclaimerWrapperToEml": false,
  "DiagnosticsAggregationServicePort": 9710,
  "EnableExternalHTTPMailDelivery": false,
  "ExternalDsnReportingAuthority": null,
  "ExternalPostmasterAddress": null,
  "HygieneSuite": "Premium",
  "InternalDsnReportingAuthority": null,
  "JournalArchivingEnabled": false,
  "JournalMessageExpirationDays": 0,
  "JournalReportDLMemberSubstitutionEnabled": false,
  "LegacyArchiveJournalingEnabled": false,
  "LegacyArchiveLiveJournalingEnabled": false,
  "LegacyJournalingMigrationEnabled": false,
  "MaxAllowedAgentGeneratedMessageDepth": 3,
  "MaxAllowedAgentGeneratedMessageDepthPerAgent": 2,
  "MaxDumpsterSizePerDatabase": "18 MB (18,874,368 bytes)",
  "MaxDumpsterTime": "7.00:00:00",
  "MessageExpiration": "1.00:00:00",
  "MigrationEnabled": true,
  "OrganizationFederatedMailbox": "FederatedEmail.4c1f4d8b-8179-4148-93bf-00a95fa1e042@contoso.com",
  "OtherWellKnownObjects": [],
  "PreserveReportBodypart": true,
  "PreventDuplicateJournalingEnabled": false,
  "QueueDiagnosticsAggregationInterval": "00:01:00",
  "RedirectDLMessagesForLegacyArchiveJournaling": false,
  "RedirectUnprovisionedUserMessagesForLegacyArchiveJournaling": false,
  "SupervisionTags": [
    "Allow",
    "Reject"
  ],
  "TLSReceiveDomainSecureList": [],
  "TLSSendDomainSecureList": [],
  "TransportRuleAttachmentTextScanLimit": "1 MB (1,048,576 bytes)",
  "TransportRuleCollectionAddedRecipientsLimit": 100,
  "TransportRuleCollectionRegexCharsLimit": "20 KB (20,480 bytes)",
  "TransportRuleConfig": "TransportRuleCollectionAddedRecipientsLimit:100 TransportRuleLimit:300 TransportRuleCollectionRegexCharsLimit:20 KB (20,480 bytes) TransportRuleSizeLimit:8 KB (8,192 bytes) TransportRuleAttachmentTextScanLimit:1 MB (1,048,576 bytes) TransportRuleRegexValidationTimeout:00:00:00.3000000 TransportRuleMinProductVersion:14.0.0.0",
  "TransportRuleLimit": 300,
  "TransportRuleMinProductVersion": "14.0.0.0",
  "TransportRuleRegexValidationTimeout": "00:00:00.3000000",
  "TransportRuleSizeLimit": "8 KB (8,192 bytes)",
  "VerifySecureSubmitEnabled": false,
  "Xexch50Enabled": true
}

Notes: transportConfig is a tenant singleton: there is exactly one instance per organization and it is addressed without a key. The backing Get-TransportConfig cmdlet returns no Identity argument.

PATCH /exchange/v1.0/transportConfig

Partial update of the transportConfig singleton via Set-TransportConfig. Body keys map 1:1 to cmdlet params (camelCased). Returns 200 + the post-Set entity.

TENANT-WIDE impact - changes tenant defaults that every recipient inherits unless overridden per-mailbox. Practical use cases the allowlist supports: tenant-wide message size limits (maxReceiveSize, maxSendSize, maxRecipientEnvelopeLimit), external postmaster address, journaling NDR routing + retention, ReplyAll-storm protection, SMTP AUTH legacy-disable, internal SMTP server header preservation, TLS legacy-client allowlist, DSN HTML formatting. The Wiki documents ~60 settable params on this cmdlet; the API exposes ~20 cloud-applicable ones (see ). On-prem replication/dumpster/shadow params (Shadow*, MaxDumpsterSizePerDatabase, MaxRetriesForLocalSiteShadow) are intentionally omitted.Singleton PATCH - no URL key. Pass ?dryRun=true for a -WhatIf preview.

Backing cmdlet: Set-TransportConfig. Role: OrganizationConfig.ReadWrite (Enterprise).

Parameter	In	Type
`addressBookPolicyRoutingEnabled`	body
`allowLegacyTLSClients`	body
`clearCategories`	body
`convertDisclaimerWrapperToEml`	body
`dsnConversionMode`	body
`externalDelayDsnEnabled`	body
`externalDsnDefaultLanguage`	body
`externalDsnLanguageDetectionEnabled`	body
`externalDsnReportingAuthority`	body
`externalDsnSendHtml`	body
`externalPostmasterAddress`	body
`headerPromotionModeSetting`	body
`internalDelayDsnEnabled`	body
`internalDsnDefaultLanguage`	body
`internalDsnLanguageDetectionEnabled`	body
`internalDsnReportingAuthority`	body
`internalDsnSendHtml`	body
`internalSMTPServers`	body
`journalingReportNdrTo`	body
`journalMessageExpirationDays`	body
`maxReceiveSize`	body
`maxRecipientEnvelopeLimit`	body
`maxSendSize`	body
`messageExpiration`	body
`preventDuplicateJournalingEnabled`	body
`replyAllStormBlockDurationHours`	body
`replyAllStormDetectionMinimumRecipients`	body
`replyAllStormDetectionMinimumReplies`	body
`replyAllStormProtectionEnabled`	body
`rfc2231EncodingEnabled`	body
`smtpClientAuthenticationDisabled`	body
`verifySecureSubmitEnabled`	body
`dryRun`	query	bool (switch)

Update tenant-wide transport configuration

Partial update of the transportConfig singleton via Set-TransportConfig. Body keys map 1:1 to the cmdlet’s cloud-applicable params (camelCased); changes are tenant-wide defaults that every recipient inherits unless overridden per-mailbox. Returns the post-Set entity.

PATCH /exchange/v1.0/transportConfig HTTP/1.1
Authorization: Bearer {token}
Content-Type: application/json

{
  "externalPostmasterAddress": "postmaster@contoso.com",
  "maxReceiveSize": "150 MB",
  "smtpClientAuthenticationDisabled": true
}

HTTP/1.1 200 OK
Content-Type: application/json; odata.metadata=minimal

{
  "Identity": "Transport Settings",
  "Id": "Transport Settings",
  "ExternalPostmasterAddress": "postmaster@contoso.com",
  "MaxReceiveSize": "150 MB (157,286,400 bytes)",
  "SmtpClientAuthenticationDisabled": true
}

Notes: Doc-derived from Wiki + write-param allowlist; not live-captured. Body fields are Wiki-valid; values are illustrative. transportConfig is a tenant singleton: PATCH takes no URL key. Pass ?dryRun=true for a Set-TransportConfig -WhatIf preview.

?dryRun=true previews of any write stay on Community.