That's cleared up several things for me. Thanks very much PaulW!

[Y]

I'm a little confused (what's new ;) ), about when the SMTP envelope is created and part of the SMTP delivery process. I have seen many references to the envelope but nothing tangible about its creation. Can anyone offer some clarification please?

In our setup Pegasus Mail creates the message and delivers it to Mercury. Mercury accepts it and creates a .101 file (or does Pegasus Mail create the .101 file?), Mercury then converts the .101 into the job queue pair and then opens those to determine where the message needs to go.

It then connects (using MercuryC), to the cloud filtering service we use which then 'filters' the message. This is where I am a little unsure about the delivery process.

Does the filtering service establish the connection to the receiving server after it has checked the message so that the EHLO etc command/response process can begin or does the filtering service tell Mercury to establish the connection once the message is considered safe for transmission?

Is the envelope created when Mercury hands the message over to the filtering service? If so, does Mercury create the envelope?

Thanks :)

[quote user="Greenman"]

I'm a little confused (what's new ;) ), about when the SMTP envelope is created and part of the SMTP delivery process. I have seen many references to the envelope but nothing tangible about its creation. Can anyone offer some clarification please?[/quote]

The envelope is a name given to the addressing part of the email message consisting of the "MAIL FROM" and "RCPT TO" SMTP commands.  It doesn't always exist as a separate identifiable part of the message, although there are usually traces of it in residual headers in the delivered message.

[quote]In our setup Pegasus Mail creates the message and delivers it to Mercury. Mercury accepts it and creates a .101 file (or does Pegasus Mail create the .101 file?),[/quote]

PMail creates the .101 file with a $$ line containing the originating address and (possibly multiple) T, C, and B lines for the destination, CC and BCC addresses.  These lines are effectively the envelope.

[quote]Mercury then converts the .101 into the job queue pair and then opens those to determine where the message needs to go.

It then connects (using MercuryC), to the cloud filtering service we use which then 'filters' the message. This is where I am a little unsure about the delivery process.

Does the filtering service establish the connection to the receiving server after it has checked the message so that the EHLO etc command/response process can begin or does the filtering service tell Mercury to establish the connection once the message is considered safe for transmission?[/quote]

This depends on the filtering service - for instance I see Messagelabs take the message and then deliver it.  You should be able to tell by looking at the headers of a message that has been sent.

[quote]Is the envelope created when Mercury hands the message over to the filtering service? If so, does Mercury create the envelope?[/quote]

Usually it will exist before the message gets to Mercury - as in your example.  If the message is an error notification or a delivery report generated by Mercury, then it will have created everything.