Many thanks for these information. I'll try asap.

Configuration is as the following :
- client Pegasus Mail
- server Mercury/32
On the user's PC PMail is configured with its main address a@domain.com and a second address b@domain.com is added.
Beside the default identity another identity B is created and associated with address b@domain.com.
Two problems occurr :
1. When a mail is sent from identity B the from information in the message header is still a@domain.com. Internet parameters for identity B are correctly set-up.
2. Sent messages from identity B are stored in the Copies to self folder of identity A.
Many thanks in advance for some help ...

[quote user="PHR"]Configuration is as the following :
- client Pegasus Mail
- server Mercury/32
On the user's PC PMail is configured with its main address a@domain.com and a second address b@domain.com is added.
Beside the default identity another identity B is created and associated with address b@domain.com.
Two problems occurr :
1. When a mail is sent from identity B the from information in the message header is still a@domain.com. Internet parameters for identity B are correctly set-up.
2. Sent messages from identity B are stored in the Copies to self folder of identity A.
Many thanks in advance for some help ...[/quote]

I'm assuming you are sending via Mercury in which case this is more of a Mercury question than Pegasus - this is how I do it:

1. In Pmail, for each identity go to Tools / Options / Sending mail and fill in "Default 'reply-to' address:" with the email for that identity. You may wish to change the "Personal name" in Basic settings as well.

2. Use PCONFIG.exe to create a user-defined gateway (UDG).  Put the Mercury queue directory in the name of the "Outgoing mail path" in \\server\sharename format so it makes sense regardless of drive letters. Change the "Filename format" to ~d~d.101.   In "Reply address format", enter "~p" <~r>  (this puts in the personal name and reply-to address set in 1). Set "Accept SMTP addresses to Y.  "Simple message headers should be 'Glue' headers. "Strip gateway name" is Y. "Force all mail through" should be Y.  All other settings can be left as the defaults.

This enables PMail to write directly to the Mercury queue and means you no longer use an SMTP definition for sending outgoing mail.