You could use SMTP to send the emails. SMTP communicates directly with the email server, bypassing Outlook completely. You can set the from address to anything you want.

http://www.topwizprogramming.com/pbnismtp.html

Have you tried supplying the optional "profile"  & "password" argument values to the mailSession.mailLogon function? I have not tried this myself (I generate emails from MS Outlook via OLE) but it might change the sender by using a non-default profile.

The PB-supplied Mail objects are adequate for simple emails, but once you need to go beyond their limited capabilities, you should use OLE if you want to send email via Outlook.

I am creating a MailSession in my PB code.

And within here declare local instances of variables

MailSession  PBMailSession

MailRecipient   PBMailRecipient
MailMessage    PBMailMessage

PBMailSession = CREATE mailSession

....

...

PBMailMessage.Subject =
PBMailMessage.NoteText =

PBMailMessage.Recipient[1].name = xxx@ebrd.com

There is no equivalent of 'MailItem object has a property SenderEmailAddress' in MailSession.

If you are using OLE to send email via Outlook, the MailItem object has a property SenderEmailAddress.

https://docs.microsoft.com/en-us/previous-versions/office/developer/office-2007/bb175525(v%3doffice.12)

If you aren't using OLE to send email via Outlook, please give more details.