Folks,

I have no experience with sendmail but want to know if its possible to
configure sendmail for SMTP namespace sharing for coexistance with a
foreign mail system. Basically I want an email to be delivered to a
mailbox on the sendmail system if it exists otherwise forward it to
another SMTP server.

Is this sort of config possible with sendmail?

cheers

Fat Tom

stuff [at] istic.co.uk writes:
> I have no experience with sendmail but want to know if its possible to
> configure sendmail for SMTP namespace sharing for coexistance with a
> foreign mail system. Basically I want an email to be delivered to a
> mailbox on the sendmail system if it exists otherwise forward it to
> another SMTP server.
>
> Is this sort of config possible with sendmail?

*It is possible*
http://www.google.com/search?q=site%3Asendmail.org+LUSER_REL AY
*but it is not recommended*
Due to "dictionary recipient" spam forwarding "all remaining" local
email addresses to another hosts is not recommended for hosts that may
receive spam from the Internet.

Could you provide more details about what you want to achieve?
[situation you face] You may want to implement "sub-optimal" solution.

--
[pl>en: Andrew] Andrzej Adam Filip : anfi [at] priv.onet.pl : anfi [at] xl.wp.pl
You should never bet against anything in science at odds of more than
about 10^12 to 1.
-- Ernest Rutherford

On 29 Aug, 11:17, Andrzej Adam Filip <a... [at] onet.eu> wrote:
> st... [at] istic.co.uk writes:
> > I have no experience with sendmail but want to know if its possible to
> > configure sendmail for SMTP namespace sharing for coexistance with a
> > foreign mail system. Basically I want an email to be delivered to a
> > mailbox on the sendmail system if it exists otherwise forward it to
> > another SMTP server.
>
> > Is this sort of config possible with sendmail?
>
> *It is possible*
> http://www.google.com/search?q=site%3Asendmail.org+LUSER_REL AY
> *but it is not recommended*
> Due to "dictionary recipient" spam forwarding "all remaining" local
> email addresses to another hosts is not recommended for hosts that may
> receive spam from the Internet.
>
> Could you provide more details about what you want to achieve?
> [situation you face] You may want to implement "sub-optimal" solution.
>
> --
> [pl>en: Andrew] Andrzej Adam Filip : a... [at] priv.onet.pl : a... [at] xl.wp.pl
> You should never bet against anything in science at odds of more than
> about 10^12 to 1.
> -- Ernest Rutherford

Ernest,

I am basically being tasked with a migration project from sendmail to
Exchange.

Email from the internet will be send via the new exchange organisation
which will be configured with appropiate SMTP domains if a mail box
for a user exists (migrated) then it will be delivered to that
mailbox. Otherwise it will be sent onwards to the sendmail SMTP
server. This should work fine until a user on the sendmail system
(not migrated) tried to send an email to a migrated user (exchange).
I'm assuming the sendmail server will do some sort of lookup against
its mailbox database decide the user doesn't exist and NDR the email.
Ideally I'd like the sendmail to send the email to the exchange server
so that can NDR the email or deliver it if the user exists. Routing
loops will be avoided as the Exchange system maintains a list off all
the users on the sendmail system.

Thoughts

Fat Tom

stuff [at] istic.co.uk writes:

> On 29 Aug, 11:17, Andrzej Adam Filip <a... [at] onet.eu> wrote:
>> st... [at] istic.co.uk writes:
>> > I have no experience with sendmail but want to know if its possible to
>> > configure sendmail for SMTP namespace sharing for coexistance with a
>> > foreign mail system. Basically I want an email to be delivered to a
>> > mailbox on the sendmail system if it exists otherwise forward it to
>> > another SMTP server.
>>
>> > Is this sort of config possible with sendmail?
>>
>> *It is possible*
>> http://www.google.com/search?q=site%3Asendmail.org+LUSER_REL AY
>> *but it is not recommended*
>> Due to "dictionary recipient" spam forwarding "all remaining" local
>> email addresses to another hosts is not recommended for hosts that may
>> receive spam from the Internet.
>>
>> Could you provide more details about what you want to achieve?
>> [situation you face] You may want to implement "sub-optimal" solution.
>
> Ernest,
>
> I am basically being tasked with a migration project from sendmail to
> Exchange.
>
> Email from the internet will be send via the new exchange organisation
> which will be configured with appropiate SMTP domains if a mail box
> for a user exists (migrated) then it will be delivered to that
> mailbox. Otherwise it will be sent onwards to the sendmail SMTP
> server. This should work fine until a user on the sendmail system
> (not migrated) tried to send an email to a migrated user (exchange).
> I'm assuming the sendmail server will do some sort of lookup against
> its mailbox database decide the user doesn't exist and NDR the email.
> Ideally I'd like the sendmail to send the email to the exchange server
> so that can NDR the email or deliver it if the user exists. Routing
> loops will be avoided as the Exchange system maintains a list off all
> the users on the sendmail system.

Assign every user extra 'internal' email address such as:
user1 [at] sendmail.example.com
user2 [at] exchange.example.com

It will allow you to use
1) on sendmail virtusertable entries:
user2 [at] example.com user2 [at] exchange.example.com
2) on exchange similar "aliases" for users hosted on sendmail
[I have forgotten MS Exchange 'terminology' ]

Such scheme will allow any of the two to act as internet email gateway.
When I administered MS Exchange server a few years ago "unscheduled
outages" was not something I could forget.

--
[pl>en: Andrew] Andrzej Adam Filip : anfi [at] priv.onet.pl : anfi [at] xl.wp.pl
A mother takes twenty years to make a man of her boy, and another woman
makes a fool of him in twenty minutes.
-- Frost

Andrzej Adam Filip wrote:
> stuff [at] istic.co.uk writes:

>> I am basically being tasked with a migration project from sendmail to
>> Exchange.
>>
>> Email from the internet will be send via the new exchange organisation
>> which will be configured with appropiate SMTP domains if a mail box
>> for a user exists (migrated) then it will be delivered to that
>> mailbox. Otherwise it will be sent onwards to the sendmail SMTP
>> server. This should work fine until a user on the sendmail system
>> (not migrated) tried to send an email to a migrated user (exchange).
>> I'm assuming the sendmail server will do some sort of lookup against
>> its mailbox database decide the user doesn't exist and NDR the email.
>> Ideally I'd like the sendmail to send the email to the exchange server
>> so that can NDR the email or deliver it if the user exists. Routing
>> loops will be avoided as the Exchange system maintains a list off all
>> the users on the sendmail system.
>
> Assign every user extra 'internal' email address such as:
> user1 [at] sendmail.example.com
> user2 [at] exchange.example.com

Hmm. I'm not sure that it isn't possible at all - but I never succeeded
in doing things like this. My exchange 2003 server would refuse this
address and complain that "exchange.example.com" is a host name and
not a mail domain. :-(

>
> It will allow you to use
> 1) on sendmail virtusertable entries:
> user2 [at] example.com user2 [at] exchange.example.com

This would not work in my domain, for the reason I mentioned above.
YMMV.

But LDAP routing will work. LDAP routing can be configured to use local
map lookups instead of LDAP queries.
If S.user [at] example.com is a sendmail user and E.user [at] example.com an
exchange user, then something like the following maps can be used to
route the mail for ... [at] example.com on the sendmail server.

The "mailHost" map:
S.user [at] example.com localhost
E.user [at] example.com exchange.example.com

And the "mailRoutingAddress" map:
S.user [at] example.com S.user [at] sendmail.example.com
E.user [at] example.com E.user [at] example.com

See the README file in the 'cf' directory of the sendmail source
for more details about LDAP routing.

> 2) on exchange similar "aliases" for users hosted on sendmail
> [I have forgotten MS Exchange 'terminology' ]
>
> Such scheme will allow any of the two to act as internet email gateway.
> When I administered MS Exchange server a few years ago "unscheduled
> outages" was not something I could forget.
>

Regards,

Kees.

--
Kees Theunissen.

Kees Theunissen <theuniss [at] rijnh.nl> writes:

> Andrzej Adam Filip wrote:
>> stuff [at] istic.co.uk writes:
>
>>> I am basically being tasked with a migration project from sendmail to
>>> Exchange.
>>>
>>> Email from the internet will be send via the new exchange organisation
>>> which will be configured with appropiate SMTP domains if a mail box
>>> for a user exists (migrated) then it will be delivered to that
>>> mailbox. Otherwise it will be sent onwards to the sendmail SMTP
>>> server. This should work fine until a user on the sendmail system
>>> (not migrated) tried to send an email to a migrated user (exchange).
>>> I'm assuming the sendmail server will do some sort of lookup against
>>> its mailbox database decide the user doesn't exist and NDR the email.
>>> Ideally I'd like the sendmail to send the email to the exchange server
>>> so that can NDR the email or deliver it if the user exists. Routing
>>> loops will be avoided as the Exchange system maintains a list off all
>>> the users on the sendmail system.
>>
>> Assign every user extra 'internal' email address such as:
>> user1 [at] sendmail.example.com
>> user2 [at] exchange.example.com
>
> Hmm. I'm not sure that it isn't possible at all - but I never succeeded
> in doing things like this. My exchange 2003 server would refuse this
> address and complain that "exchange.example.com" is a host name and
> not a mail domain. :-(

I few years ago I used scheme with two MS Exchange servers
"organization" and two sendmail gateways delivering messages
via SMTP directly to MS Exchange server holding the mailbox.
Every MS Exchange user mailbox had two email addresses:
user1 [at] example.com & user1 [at] office1.example.com
user2 [at] example.com & user2 [at] office2.example.com

May be The Bill has made something to make it no longer possible ;-)

>> It will allow you to use 1) on sendmail virtusertable entries:
>> user2 [at] example.com user2 [at] exchange.example.com
>
> This would not work in my domain, for the reason I mentioned above.
> YMMV.

I doubt you are right but I no longer administer MS Exchange "servers"
so I can be 100% sure.

> But LDAP routing will work. LDAP routing can be configured to use local
> map lookups instead of LDAP queries.
> If S.user [at] example.com is a sendmail user and E.user [at] example.com an
> exchange user, then something like the following maps can be used to
> route the mail for ... [at] example.com on the sendmail server.
>
> The "mailHost" map:
> S.user [at] example.com localhost
> E.user [at] example.com exchange.example.com
>
> And the "mailRoutingAddress" map:
> S.user [at] example.com S.user [at] sendmail.example.com
> E.user [at] example.com E.user [at] example.com
>
> See the README file in the 'cf' directory of the sendmail source
> for more details about LDAP routing.

Use of ldap_routing (with or without LDAP) is another of *many* possible
ways to manage "staged migration" in mailbox by mailbox way with
ability to reject invalid addresses in incoming SMTP sessions.

BTW ldap_routing without LDAP frequently uses "null" map for one of the
two maps used by ldap_routing.
[ "null" map returns *always* "no match" (nothing found) ]

>> 2) on exchange similar "aliases" for users hosted on sendmail
>> [I have forgotten MS Exchange 'terminology' ]
>>
>> Such scheme will allow any of the two to act as internet email gateway.
>> When I administered MS Exchange server a few years ago "unscheduled
>> outages" was not something I could forget.
>
> Regards,
>
> Kees.

--
[pl>en: Andrew] Andrzej Adam Filip : anfi [at] priv.onet.pl : anfi [at] xl.wp.pl
Perhaps the remembrance of these things will prove a source of future
pleasure.
-- Virgil