Discussion of OCP/SMTP profile
and some Use cases
Presented by
Abbie Barbir
abbieb@nortelnetworks.com
OCP Recap
August 3, 2004 2
OCP Building Blocks
August 3, 2004 3
OCP/SMTP Profile
• Defines a profile for the OCP core that allows to handle
SMTP messages
• OCP has a feature to negotiate profiles between client and
server
• SMTP profile may have additional parameters/options that
can be used in the negotiation process
• Focus is on adaptation of RFC 2822 formatted email
messages
August 3, 2004 4
Uses Cases 1/2
Use Case 1:
• MTA at a corporate gateway handles outgoing mail traffic
• In "MAIL FROM:" command it gets the sender's email
address
• Before replying to this command (allow/deny) it sends an OCP
request to an OPES service that checks in the corporate
directory service whether that employee is allowed to send
mails to the Internet
• Depending on the OCP response the MTA replies in the SMTP
dialog with allow or deny
Use Case 2:
• The other way around
• The MTA sends OCP requests for all "RCPT TO:" commands
for incoming messages and asks the OPES service whether the
recipient exists and is allowed to receive email
August 3, 2004 5
Uses Cases 2/2
Use Case 3:
• Sender validation via OPES
• OPES service checks sender IP, HELO command, resolves
the sender address etc.
• This may tell the MTA not to accept the message for
delivery
• Could even be done asynchronously for some parts, i.e.
sending the OCP request after HELO or MAIL FROM and
continuing to handle recipients and to receive the mail
body
• The response needs to be there before the message gets
finally accepted
August 3, 2004 6
OCP/SMTP Profile …
• Some metadata from the SMTP dialog may need to be
transferred from the OCP client to the OCP Sever e.g.
– The values of the "MAIL FROM" and "RCPT TO"
commands are often needed to determine the real sender
and recipient of the messages (not relying on the visible
data in the email message header)
– Need to define the extent of the SMTP profile for OCP and
decide if it is allowed to adapt SMTP commands
themselves
August 3, 2004 7
Which SMTP element?
• WG will focus on Message Transfer Agent (MTA) to be the
first target for OCP client implementers
• Need to determine whether this can/should be extended to
usage in
– Mail user agent (MUA)
– Mail Submission Agent (MSA)
August 3, 2004 8
Some Open Issues/Problems
• SMTP messages can have multiple recipients
• The callout server may need to apply different filtering
policies to different recipients
• For example: The callout server does language translation to
the native language of the recipient
• If a message from an English sender is sent to two French and
one German recipients, two copies of the message are needed
• The OCP callout server has to tell the OCP client that multiple
copies will be returned and to which recipient a copy should be
sent
• An additional problem is the creation of end use error
messages, if these messages are not only sent to the recipients
but also to the sender and/or postmaster
August 3, 2004 9
Some Open Issues/Problems…
• WG needs to decide whether the creation of a MIME profile
could be a side effect of the SMTP profile work or whether the
SMTP profile can be structured in a way that allows easy
definition of OCP/MIME at a later time
• Need to determine how this will fit with IAB consideration for
OPES RFC, for example:
– How tracing will be addressed
– Tracking of performed adaptations/Bypass
• Privacy Issues
August 3, 2004 10
Q&A
August 3, 2004 11