Each DDE transaction type has a receiver and an associated activity that causes the DDEML to generate each type.
| Transaction type | Receiver | Cause |
| XTYP_ADVDATA | Client | A server responded to an XTYP_ADVREQ transaction by returning a data handle. |
| XTYP_ADVREQ | Server | A server called the DdePostAdvise function, indicating that the value of a data item in an advise loop had changed. |
| XTYP_ADVSTART | Server | A client specified the XTYP_ADVSTART transaction type in a call to the DdeClientTransaction function. |
| XTYP_ADVSTOP | Server | A client specified the XTYP_ADVSTOP transaction type in a call to DdeClientTransaction. |
| XTYP_CONNECT | Server | A client called the DdeConnect function and specified a service name and topic name supported by the server. |
| XTYP_CONNECT_CONFIRM | Server | The server returned TRUE in response to an XTYP_CONNECT or XTYP_WILDCONNECT transaction. |
| XTYP_DISCONNECT | Client/Server | A partner in a conversation called the DdeDisconnect function, causing both partners to receive this transaction. |
| XTYP_ERROR | Client/Server | A critical error has occurred. The DDEML may not have sufficient resources to continue. |
| XTYP_EXECUTE | Server | A client specified the XTYP_EXECUTE transaction type in a call to DdeClientTransaction. |
| XTYP_MONITOR | DDE monitoring application | A DDE event occurred in the system. For more information about DDE monitoring applications, see Monitoring Applications. |
| XTYP_POKE | Server | A client specified the XTYP_POKE transaction type in a call to DdeClientTransaction. |
| XTYP_REGISTER | Client/Server | A server application used the DdeNameService function to register a service name. |
| XTYP_REQUEST | Server | A client specified the XTYP_REQUEST transaction type in a call to DdeClientTransaction. |
| XTYP_UNREGISTER | Client/Server | A server application used DdeNameService to unregister a service name. |
| XTYP_WILDCONNECT | Server | A client called the DdeConnect or DdeConnectList function, specifying NULL for the service name, the topic name, or both. |
| XTYP_XACT_COMPLETE | Client | An asynchronous transaction, sent when the client specified the TIMEOUT_ASYNC flag in a call to DdeClientTransaction, has concluded. |