[Exim] Some general questions regarding Exim (New here)

Good morning everyone.

I'm new to this list as well as Exim. Being so, I have some questions that
I want to ask regarding exim.

I'm working on a particular setup with cyrus-imapd that requires the use of
bulletin boards and shared folders and control through ACL's. Originally, I
was going to use Postfix for this (MTA I am familiar with) but Postfix will
not do this because when the MUA authenticates to the MTA, the authid is
passed along to lmtpd in the AUTH= keyword in the MAIL FROM command. lmtpd
then checks to see if this authid has posting rights on the rcpt
mailbox. Without the authid given by the MTA, lmtpd assumes that the
authid is "anonymous", which means you would have to grant anyone posting
rights on the mailbox, which is what I am trying to avoidis trying to avoid.

Postfix does not pass the authid to the lmtpd process, hence ACL's will not
work for what i want to do. Now, I know sendmail will do it, but im not
sure if I want to use sendmail. The other MTA that I was told that could do
it is Exim.

Now, I have heard of Exim, but never used it and so I was hoping I could
get some feedback on the following questions:

- configuration. How is the syntax? Is it easy to ready, or like sendmail,
cryptic?
- security.
- stability
- scalability
- the ability to interface with 3rd party virus scanners (vexitra, sophos etc.)
- anti-spam checking, rbl checks etc.

Basically, im trying to get a general overall feel for Exim to see if it is
a good possibility for me.

Feel free to email me personally with your experiences, opinions etc. I
always look forward to hearing from others on a specific product im not
familiar with.

I appreciate it.

Jason