Marc Perkel wrote:
> Quick question. What variable holds the HELO greeting send when someone
> connects? rying to find what to set so that the HELO matches the RDNS of
> the interface address.
>
The default is the machine's 'hostname' ELSE the hostname set in
~/exim/configure, such as:
primary_hostname = VIRTHOST
smtp_active_hostname = SENDHOST
Note that as-shown I map mine to a MACRO - which in turn can be set by
reading in a file. This to make portability of the confugure file easier.
When sending, you can use the 'helo_data' variable to match a helo
string to each of several domains hosted.
*HOWEVER* ..
'none of the above' will alter what a far-end turns up on an rDNS call.
IF the far-end actually makes such a call (not all MTA do so).
What (usually) happens when they do, is that your furnished helo string
will appear, AND that returned from the DNS PTR RR for the IP from
whence you conected.
Note that that is a process independent of YOUR MTA...
So long as you have ONE, and only ONE <domain>.<tld> with a PTR RR
mapped to a single given IP, AND use the *same* helo string, and/or the
correct one for each of several IP with only one PTR RR each, they will
match.
IF, OTOH, you map more than one <domain>.<tld> to one IP, as is
permitted, especialy for multi-domain mail services, then it is a pure
dice-roll. Most of the time they will NOT match, because the far-end's
call is answered more or less round-robin or randomized, so that even if
all such RR's are presented it may 'see' only the first one furnished.
Finally - it requires a bit of finagling to get Exim to use a specific
IP for outbound, and more yet to insure that it uses the desired IP for
each of several multiple messages coming off the queue at a given
queue-runner pass.
Then there are retries.
Bottom line:
When serving multiple domains, it may be best to use just one
'mothership' domain that has the correct DNS entries, but is otherwise
not matched to ANY of the client's domains.
Next best - if your client *must* have end-to-end 'corporate identity'
is to run separate instances of Exim on separate IP's, one per each such
client.
HTH,
Bill Hacker
