ENABLING COMMUNICATION BETWEEN SOURCE AND TARGET MAIL TRANSFER AGENTS

• US 20130238715A1
• Filed: 03/07/2012
• Published: 09/12/2013
• Est. Priority Date: 03/07/2012
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Sanyal, Shubhankar, Gourevitch, Gregory, De Graaf, Wilbert
• Granted Patent: US 9,048,428 B2
• Time in Patent Office: Days
• US Class Current: 709/206
• CPC Class Codes: H04L 51/00 User-to-user messaging in packet-switching networks, transmitted according to store-and-forward or real-time protocols, e.g. e-mail
• CPC Class Codes: H10K 99/00 Subject matter not provided for in other groups of this subclass

Abstract

A system is provided for enabling a source MTA to communicate with a target MTA via an SMTP proxy using SMTP commands for transmitting email messages in a networked environment. An email message may be received by a source mail transport agent (MTA) and the source MTA may route the incoming email message to a target MTA via an SMTP proxy. The SMTP proxy may serve as an intermediary proxy server for enabling the source MTA to communicate with an external and internal target MTA. The SMTP proxy may connect to a target MTA via a connection command, and the SMTP proxy may implement custom SMTP commands to communicate additional information about the source MTA to the target MTA. The system may additionally enable the SMTP proxy to perform actions designated by the SMTP commands and to communicate the result of the SMTP proxy'"'"'s actions back to the source MTA.

Claims

1. A method executed at least in part in a computing device for enabling communication between source and target mail transfer agents (MTAs), the method comprising:

receiving an email message at an in-network MTA;

enabling establishment of a connection with an out-of-network MTA through a Simple Mail Transfer Protocol (SMTP) proxy server; and

controlling a behavior of the SMTP proxy server by the in-network MTA through one or more proxy commands exchanged between the in-network MTA and the SMTP proxy server, and between the SMTP proxy server and the out-of-network MTA.

2. The method of claim 1, further comprising:

employing an XPROXYTO command from the in-network MTA to the SMTP proxy server to indicate at least one from a set of;

the out-of-network MTA, a port to proxy to, a security certificate, an SMTP extension to be employed, and a mail risk parameter.

3. The method of claim 2, wherein the mail risk parameter enables the SMTP proxy server to select a public in-network IP address for use in connecting to the out-of-network MTA.

4. The method of claim 2, further comprising:

upon successful completion of tasks specified by the XPROXYTO command at the SMTP proxy server, exchanging an EHLO/HELO command set between the SMTP proxy server and the out-of-network MTA;

upon receiving out-of-network MTA responses to requests specified by the in-network MTA, providing an XPROXYTO response to the in-network MTA that includes one or more options advertised by the out-of-network MTA; and

if the out-of-network MTA options are acceptable to the in-network MTA, receiving email data from the in-network MTA at the SMTP proxy server for delivery to the out-of-network MTA.

5. The method of claim 4, further comprising:

if connection between the SMTP proxy server and the out-of-network MTA is severed during the delivery of the email data, reporting to the in-network MTA;

terminating the session at the in-network MTA; and

attempting a reconnect session through one of the SMTP proxy server and another SMTP proxy server to the out-of-network MTA employing the XPROXYTO command.

6. The method of claim 1, further comprising:

upon receiving a message at the SMTP proxy server from the out-of-network MTA, accepting commands until an actual transmission of message data and storing received information in SMTP proxy server memory;

determining a target in-network MTA to proxy to;

replaying to the target in-network MTA the commands received from the out-of-network MTA.

7. The method of claim 6, further comprising:

inserting an XPROXYFROM command that communicates information about the out-of-network MTA to the target in-network MTA.

8. The method of claim 7, wherein the SMTP proxy server decides not to proxy the received message if it determines options advertised to the out-of-network MTA are not available on the target in-network MTA.

9. The method of claim 1, wherein the SMTP proxy server is configured to act as one of a level 4 proxy layer and a level 7 proxy layer during data exchange between the in-network MTA and the out-of-network MTA.

10. The method of claim 1, further comprising:

providing an endpoint for an end user mail user agent (MUA) at the SMTP proxy server to submit an authenticated message without having to know which MTA is to process the message, wherein the SMTP proxy server determines which MTA to proxy the message to.

11. The method of claim 10, further comprising:

determining, at the SMTP proxy server, which in-network MTA is to process the message sent from an authenticated user based on an identity of the user as determined by the authentication;

connecting the MUA of the authenticated user to the in-network MTA; and

employing an XPROXY command to communicate information about the MUA to the in-network MTA.

12. A server for enabling communication between source and target mail transfer agents (MTAs), the server comprising:

a memory storing instructions;

a processor coupled to the memory, the processor executing a Simple Mail Transfer Protocol (SMTP) proxy application, wherein the SMTP proxy application is configured to;

receive an email message at an in-network MTA;

establish a connection with an out-of-network MTA;

enable control of a behavior of the SMTP proxy application by the in-network MTA through one or more proxy commands exchanged between the in-network MTA and the SMTP proxy application, and between the SMTP proxy application and the out-of-network MTA;

employ an XPROXYTO command from the in-network MTA to the SMTP proxy application to indicate at least one from a set of;

the out-of-network MTA, a port to proxy to, a security certificate, an SMTP extension to be employed, and a mail risk parameter; and

upon receiving a message at the SMTP proxy application from the out-of-network MTA, employ an XPROXYFROM command to communicate information about the out-of-network MTA to the target in-network MTA.

13. The server of claim 12, wherein the SMTP proxy application is further configured to:

provide an endpoint for an end user mail user agent (MUA) to submit an authenticated message without having to know which MTA is to process the message;

employ an XPROXY command to communicate information about the MUA to the in-network MTA; and

determine the in-network MTA to process the message sent from an authenticated user based on an identity of the user as determined by the authentication.

14. The server of claim 12, wherein the SMTP proxy application is further configured to:

upon receiving out-of-network MTA responses to requests specified by the in-network MTA, provide options advertised by the out-of-network MTA in an XPROXYTO response to the in-network MTA;

if the out-of-network MTA initiates the message, provide requests advertised by the out-of-network MTA to the in-network MTA in the XPROXYFROM command; and

terminate proxying the message received from the out-of-network MTA, if the requests advertised by the out-of-network MTA are not available on the target in-network MTA.

15. The server of claim 14, wherein the server is in one of a cloud-based architecture, a server-client architecture, and a distributed service architecture.

16. The server claim 15, wherein the SMTP proxy application is further configured to:

employ a plurality of XPROXYTO commands based on a comparison of parameters included in the XPROXYTO command to one or more sizes defined by one of a network and an SMTP proxy setting.

17. The server of claim 16, wherein the SMTP proxy application is further configured to:

employ a “

last”

parameter indicating that an XPROXYTO command that includes the “

last”

parameter is the last command in a sequence of XPROXYTO commands.

18. The server of claim 12, wherein the SMTP proxy application is further configured to:

employ a session ID to identify the connection between the in-network MTA and the out-of-network MTA in at least one of the XPROXYTO and XPROXYFROM commands.

19. A computer-readable memory device with instructions stored thereon for enabling communication between source and target mail transfer agents (MTAs), the instructions comprising:

receiving an email message at an in-network MTA;

enabling establishment of a connection with an out-of-network MTA through a Simple Mail Transfer Protocol (SMTP) proxy server;

controlling a behavior of the SMTP proxy server by the in-network MTA through one or more proxy commands exchanged between the in-network MTA and the SMTP proxy server, and between the SMTP proxy server and the out-of-network MTA;

employing an XPROXYTO command from the in-network MTA to the SMTP proxy server to indicate at least one from a set of;

the out-of-network MTA, a port to proxy to, a security certificate, an SMTP extension to be employed, and a mail risk parameter;

upon receiving a message at the SMTP proxy server from the out-of-network MTA, employing an XPROXYFROM command to communicate information about the out-of-network MTA to the target in-network MTA; and

providing an endpoint for an end user mail user agent (MUA) at the SMTP proxy server to submit an authenticated message without having to know which MTA is to process the message and employing an XPROXY command to communicate information about the MUA to the in-network MTA.

20. The computer-readable memory device of claim 19, wherein the SMTP proxy server is employed to filter outbound messages.