[ydl-gen] Re: Setting up sendmail to send mail (via SMTP)

[pstreibig]

Eric Dunbar wrote:
> On 16/08/06, Eric Dunbar <eric.dunbar at gmail.com> wrote:
>> Hello all, I'm trying to make my server a little more user-friendly 
>> for my
>> friends and for that to  happen I need to add the ability for the 
>> server to
>> SEND mail.
>>
>> My ISP (Bell Sympatico) blocks all attempts to deliver mail directly to
>> another mail server. The only way for me to get mail out is by 
>> connecting to
>> my ISP's mail SMTP mail server using a username and password, over SSL.
>>
>> Does anyone have any idea how to set sendmail (or another MTA) up on 
>> YDL to
>> send mail from the server (a Gallery installation, to be specific) to a
>> public internet address?
>>
>> I've searched far and wide for this but the language surrounding 
>> sendmail is
>> quite technical (beyond my geek skills) [I don't know what question 
>> to ask
>> of Google yet ;-P].
>
> Well, I managed to answer my own question by stumbling on the right
> web page at sendmail's site:
> <http://www.sendmail.org/~ca/email/auth.html> under the section 'Using
> sendmail as a client with AUTH'.
>
> On a hunch I changed an extra setting alongside the preferences
> settings. Using the Webmin sendmail interface I made the following
> additional change:
>
> Change #1 (not listed at page cited above):
> "Send outgoing mail via host" is now set to my ISP's mail server (in
> my case: smtphm.sympatico.ca
>
> ... although, it may actually be referenced in this paragraph on that
> page (just Webmin provides an easier way to get at it ;-):
>
> " Note: if FEATURE(`authinfo') is used, then the hostname in the map
> entry must match exactly the hostname of the ISP mailserver as
> explained in cf/README: Note: searches for domain parts or IP nets are
> only performed if the access map is used; if the authinfo feature is
> used then only up to three lookups are performed (two exact matches,
> one default)."
>
> Change #2:
> Modified in the file in the middle was
> dnl define(`SMART_HOST',`smtphm.sympatico.ca')
>
> Added to the file at the end was...
>
> 1. define(`SMART_HOST',`smtphm.sympatico.ca')dnl
> 2. define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5
> LOGIN PLAIN')dnl
> 3. FEATURE(`authinfo',`hash /etc/mail/auth/client-info')dnl
>
> NOTE:  lines 1 and 2 at the end are DUPLICATES of lines in the file
> (origina linel #2 is exactly the same as the default). Could this
> duplication cause problems (right now it seems to be working nicely)?
DANGER!
Be extra careful here with your sendmail settings once you implement 
this. Unless you are locking down access to your sendmail (for your 
friends) you could be creating an open relay.  This could be considered 
a breach of contact by your ISP, and cause other nastiness such as bots 
relaying spam through your authenticated to ISP connection.

That being said, I believe sendmail reads it's configs the same way 
postfix does (which i am familiar with using).  If this is the case, 
then having a duplicate entry should not matter.  Grouping your changes 
at the end of the config will make your life easier than having to 
search throughout the entire config file.  Just for your own sanity you 
should note why you made the changes. 

I'm curious though, when you say your ISP blocks all outbound mail.  How 
are they implementing this?  I guess it's more academic curiosity, but 
did you try changing the default port for sendmail?  There are more 
reasons for not doing this than for doing it though, not the least of 
which being the pain of maintaining an up to date, fully patched secure 
mail server, which ideally your ISP is doing for you already.

cheers,
:ps