Yes it is clear for me and I looks for P-B-S but it is different case...
I just explain...
We use ISPConfig for many years (great tools - Thanks a lot) but now one of our domains must be hosted on google apps (our company split to sub-company and they want to use google apps as a mail services). And now story starts. As you may know Google put Sender SMTP header filed to any mail and it looks terrible in outlook e.g. "sales on behalf of firstname.lastname@example.org
". Google confirm that is not a "business" behaviour and allow to use own SMTP (simple option in menu) to put any Sender filed. You just put SMTP address and login and password
for user (to authenticate) and you could send mails via your SMTP. And this solution is good but... not to the end.
In my case I must take care of two user database - one of google apps and second on ISPConfig (to use it as SMTP server). I must also remember to synchronized them... so I wonder how to use and configure "SMTP authentication via Google IMAP server".
In this case I could have a lot of domains on ISPConfig and one small on Google Apps but without duplicated user database.
and this is a problem