FAilover mail server

Hi i am open to any Windows or linux related solution as long as i don't have to pay anything extra..

We got one mail server currently running on SBS 2003 with Exchange

So time to time i need to take this server down as for maintenance.

There for I am looking for a solution  when the main mail server will be down example for 1 hour, in this 1 hour if any email comes it will store to another mail server, and when our main mail server will be up, all email will be transferred from Backup mail server to primary mail server,

right now i got in my hand :

(a) I have another server (SBS 2008) which is located on a different public ip , If i use 2 mx record , when 1 mx record will go down, email will go to another mx record which is SBS 2008, but I dont know how to sent those emails back to main mail server when main mail server will be up

(b) I am open to any linux base open source solution .

Thanks for your suggestions

Please i would not prefer to pay for this solution . i know you can pay some company for this service which i don't want.

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You need to create smtp connectors between mail server 1 and backup mail server 2..

Above article shows quite a bit of information and should lead you down the right trail. I also came across several Microsoft articles pertaining to ETRN..
You can use your domain provider as backup MX - most domain providers give it for free anyways.
Use one of your linux system and configure the domain as an ETRN if possible. I.e. the server will accept the emails, but will still see them as remote i.e. will not try to deliver them to a locally to a mailbox.
Configure an SMTPROUTE/transport for the domain to point to the IP of the exchange server.  When the exchange comes up, the emails will either be auto-sent (exchange issues ETRN command) or based on the queue.

I'm surprised you do not already have a linux box as a mail gateway that provides anti-virus/anti-spam/anti-adware scanning capabilities.

There are many examples on linux mail gateway setup using postfix, qmail, etc.

Note: make sure the queue time (the duration of time that the mail server will continue to attempt to deliver a message should be two days -three days)
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Will SzymkowskiSenior Solution ArchitectCommented:
I would recommend having a load balancing solution. If you are going to bring another server into the picture this would be the best way (in my opinion). If you are load balancing servers, if setup properly you should be able to take one exchange server offline and have no adverse affect on your users.

Take a look at the following links as they will help you with this solution...
fosiul01Author Commented:
I was reading that link aswell, seems like thats a good solution ...
Because : we have SBS 2008 ( trial version this moment but if needs we can buy licence )

But question is : do i have to create Same user name in this SBS 2008 (Backup server ) as Main server ?? or without creating any username  same as main Server will do the job ??

@Mkris9 My isp does not do that ...

@arnold ...

Will you be able to sent me some more information as this concept is little bit new to me . As i will prefer linux ...  I might go for this solution , it will save us to by Microsoft licence!!

I'm surprised you do not already have a linux box as a mail gateway that provides anti-virus/anti-spam/anti-adware scanning capabilities.
We  have this service, we using Sohos for Email Security/Spam control and antivirus which is sitting on Main Email server.

@~Spec01 that a good idea.. but which means i will have to buy a new Server which will cost us , server + Microsoft licence
Setting up the gateway will offload most of the processing from the exchange server.
In effect you will be something like the commercial products from postini (now google) to the various other similar services that provide front end filtering prior to forwarding the emails to your servers.

You could setup two of these to distribute the load. Note to make sure you have enough mail queue storage space based on the amount of emails your exchange processes.

All one has to do is search for "mail gateway for exchange."
fosiul01Author Commented:
I am good in send mail... so please send me some for sendmail!!!

fosiul01Author Commented:
also : i am not thinking of mail filtering .

What i am thinking is :

i will put one Exchange/Sendmail/Postix in public ip
and main mail server would be on public ip :

so when main mail server or public ip will be down... all email will go to . when main server will be up it will copied over to main server

now please bare in mind :

We have public folder on Exchange server , so how those email for those public folder will work ???


The same rules that exist for other you merely need to replicate with sendmail.
i.e. add a milter that handles the anti-virus/anti-spam.

The rest is defining the domain as handled by the server, but do not configure the domain in the virtual table nor as a local domain.

I would suggest you consider going to the other mail servers postfix/qmail/etc. They are comparatively less resource intensive as compared to sendmail and IMHO, easier to handle. I.e. instead of a single binary that handles all things, the others have the services broken up into several binaries where each handles one task. i.e. if you do not need pop/imap access, you do not start that process preserving/limiting memory and cpu use.

I think ETRN exists on sendmail.

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The emails will just be sitting in a queue on the linux backup mail servers. The messages can and will only be processed by the exchange server.

                                       / Primary Exchange server          \
message <=> Internet <=                                                   \
                                      \ Secondary linux server Queue only

I.e. if exchange is down, based on the MX, the message will be delivered to the linux box which will in turn try to connect to the exchange port 25 to deliver the message.
Make sure not to define the linux gateway server as a trusted source on the exchange server. If you do not do any anti-virus/anti-spam checks on the linux side, you want those processes on the exchange to kick in whether a connection is external to your network or from the linux gateway system/s.
fosiul01Author Commented:
ok I will read those fully

but in exchange server we got  public folder,so emails for those public folder will be stroed in sendmail/postfix then will be transfer to the Exchange server , its not it ???

and i dont have to create any username and password in sendmail or postfix  same as Exchange server

is that right ??

Emails sent to will be handled the same way by the gateway mail server. They will be accepted and queued for delivery to the primary exchange server.  There is no processing of the email by the gateway mail server unless you add the anti-virus/spam/etc/ checks.

You can use AD integration if you want, but it is not required.  The only draw back is that your gateway will accept all emails destined for the domain without regard to the username. It will not have a way to check whether the username exists.

Think of the postfix/sendmail as the mailbox for a residence/business.
The distribution of the mailings among the inhabitants will have to be done whether the mailing was handed directly to an individual or was dropped in the mailbin.
A delivery of items addressed to various individuals/departments is delivered, if the person charged with handling the distribution is present, the person accepts the delivery and starts the distribution process. If the person is not present, there is a Large container with Label: Drop Mailing/Items Here!"
When the person returns, the person accesses the large container and starts distribution of the items.

The person is the exchange.
The large container is the sendmail/postfix configured in a backup MX role.

In a gateway setup,
intenet <=> gateway Mail server <=> Exchange
Everything external flows into the gateway/Large container and then processed/handled by exchange.
i.e. person only distributes items from the large container.

Note that this only deals with emails sent to your domain.  Individuals within the firm trying to send/receive emails or access public folders during the downtime, will get errors since they can not contact the server.

fosiul01Author Commented:
Sorry for late reply., I was working with another project

but I have done this by using sendmail which works fine for me
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