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Advice required on independent SMTP servers

Posted on 2007-11-15
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We have a client on a shared server (we host his domain). Incoming mail is from our server but SMTP is to his ISP.  He needs business continuity and we are not in a position to guarantee his email sending if our office is closed and there are problems with our server. He currently has 2 broadband connections and has instructions to switch the smtp settings when he switches broadband providers if his service fails etc.

He uses outlook express and currently the smtp server is of his ISP (of the backup ISP as appropriate). He has had issues recently with them (significant delays in emails getting to his clients).

He has asked us to advise him on the best way forward and I said I would look into independent smtp servers - so this setting stays fixed in Outlok Express even if he moves between his 2 broadband providers. Not sure how these work in that if one server goes down are there providers who have redundancy built in with smtp servers to fall back on? (did not seem to be the case with his ISP).

So, providing the reasoning above is correct, any recommendations for paid smtp services to help him out.

thanks
David

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Question by:rutlandict
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by:moorhouselondon
ID: 20292048
Difficult to rely on any service unless there is a well-defined SLA in place.  I recommend to customers that they host their own mail server.  Mdaemon is the product I would suggest:-

www.altn.com
www.zensoftware.co.uk
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by:rutlandict
ID: 20311699
Great thanks.
This can be installed on a WIndows PC?
We woudl presumably recommend he has a separate machine for this - aeffectively a mail server - to give continuity or availability of the mail server.

A few questions (points raised)

1. I assume a fixed/static IP address would be needed.
Is it then just a case of setting the mail server (MX record) to the IP address and it will work?

2. Also, would this allow synchronised use of Outlook e.g. a user has Outlook setup on 2 PCs to the same MDaemon account. If he deletes an email from the inbox on one PC it will be deleted automatically on the other PC?
In other words does it work like Outlook does with Exchange.

3. Is there any way of making use of this email software and having 2 mail servers so if the first one goes down (or the broadband conenction it is linked to goses down), the 2nd one kicks in. I assume we would have to ensure the same accounts would be replicated across the 2 mail servers.
If this is possible, how woudl his Outlook be configured to "switch" to the backup email server?

thanks
David

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by:moorhouselondon
ID: 20315158
Yes it is not even obligatory to have it on a pc whose sole purpose is as a mail server (but it helps if it is.

1. Yes, I would strongly advise a Fixed IP.  You could use Dynamic DNS service to find the current address (if dynamic is used), but it's one more thing that can go wrong, one more thing to consider when troubleshooting.  Is it then just a case...?  Yes, but you will need to forward port 25 from the router to point to your mail server.  If you are going to use external POP clients then you will need port 110 forwarded, and ditto Worldclient - port 3000.

2. If you use IMAP then most definitely (you will need Mdaemon Pro for IMAP).  

3. Not sure what AltN would say about the licencing aspects of this, email them and see what they say.  Technically it is possible, but the mail store needs to be replicated periodically from one mail server to the other.  You would need to use a DNS name to refer to the mail server so that bringing the "spare" on line assumes the DNS name of the primary server - otherwise you will need to go round all your Outllooks changing the IP address in the IMAP/SMTP settings.  Port forwardinng on the router would also need to be slewed across (cos it uses IP address to refer to the target).  Another way would be to swap IP addresses of the two email servers - simpler!
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by:moorhouselondon
ID: 20315179
BTW the mail store is easy to find, easy to copy.  Every individual message is a separate file - some will argue that is bad from a performance angle, but I feel much happier with this mode of storage.
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by:rutlandict
ID: 20315253
Thanks again. I have explored this idea of backup servers before on Experts Exchange and never really got to the point of satisfying a quite comment request/assumption about redundancy with email servers.

Surely there are businesses out there who have critical email requirements and so if one email server goes down, anotherr automatically kicks in?
Maybe this is not possible? It is what I always thought was achieved by "mirrored" servers for internal LAN domains.
Your latest answer suggests a manual intervention is required if amail server goes down - whereas our client is asking for a solution which has a failsafe, rather like RAID on a PC where if one hard drive fails the other takes over.

On a related issue, he recently had a problem with one of his broadband ISPs. He sent emails via their SMTP server and his clients did not receive them for 2 hours, 12 hours, and in one case 10 days. The ISP admited to "server issues" but our client's point, which I can quite understand from a user perspective, was "why doesn't the ISP have a backup server that simply kicks in if the first one has problems"?

So my question is really the same - is it not possible to use Outlook and have your supplier of mail services setup a backup server which automatically kicks in if the first one has problems.
If this is achieved with different nameservers, different server boxes, different networks, whatever, is it possible without manual intervention?

 

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by:rutlandict
ID: 20315265
sorrry that should say "common request"
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by:moorhouselondon
ID: 20315860
Having worked for a company that insisted on having "hot spare" type backups for lots of critical functions, my experiences are

(1) the device that sits between the two critical items is just as likely to fail as the two individual critical devices.  The failure mode of this device may also cause failure of the overall system.  Therefore the probabilities of failure are not something that operate additively "in parallel" but in some hopefully exponential curve which tapers off as it approaches 100%.

(2) if the failover switch works as expected you need some kind of "hysteresis" that determines that the critical item is not simply overloaded and will recover - if you don't then you will see "oscillation" of the two devices as they switch over, go online, get overloaded, go offline and switch back again.  

(3) notifying the user that something is amiss is something that is often overlooked - so the backup is online 24/7 without anyone realizing that they need to do something with the primary device.  

(4) the flow of data from device to device is not an easy thing to keep track of - what happens if the primary device comes back on line automatrically?  It's going to be lacking emails that have been collected onto the backup spare.  If the routine copying of emails from live machine to hot spare is in progress when the live machine is deactivated then the algorithm has to be able to cope with various complex scenarios.

One of my clients had a lot of problems with broadband reliability.  The mail server was more reliable than the broadband, so what I did for them was setup another broadband line with another router - the mail server serves both lines - the MX records are setup accordingly - plus there are two domains operating using different Name Servers (another point of failure).  The outgoing mail has to be switched to point to the live broadband line, but that is all that needs to be done.  The main risk for this client is that the Mains supply to the street goes down quite often (this is in Central London!!) - it went down over last weekend for about five hours.

So is it possible without manual intervention?  Not entirely, and you wouldn't want to, a human has to properly evaluate the failure they are seeing and to act accordingly, no machine can get this right 100% of the time.  Every single installation has different risk factors, so there's no universal solution either.
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by:rutlandict
ID: 20315976
This client already has a 2nd broadband line with a different router and manually changes his SMTP server entry in Outlook when he switches routers.

I was envisaging the 2 mail servers being on different networks - so they are completely unrelated. The same domain name is used on both.
mail.domain.com
mail2.domain.com

so your point about a device that sits between the 2 critical items would not apply?

Nameservers can be replicated too I understand (particularly after this weekend when 123-reg nameservers we were relying on had issues!). Both email servers could act as nameservers. Both would have a virtual site setup using the same domain and so if one failed, mail would be collected by the second.
Pop boxes could be setup for both so mail would still be received by Outlook.

The thrust of the question was seeing how SMTP could be integrated into such a situation so as not to have to manually change smtp servers (and also not rely on ISPs for their smtp services). Using MDaemon on 2 different servers to achieve redundancy with minimal manual input in the event of problems on one of the servers.

If the power fails at the office of our client (he works from home) at least his own clients will not get email bounced back - which to him looks unprofessional. He could resort to a third tier of broadband backup such as a Vodafone connect card for his laptop to allow him to still send/receive.


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moorhouselondon earned 500 total points
ID: 20316272
123-reg: yes they did have problems didn't they.

You could setup the mail servers in the way you suggested, but IMAP would then be difficult, POP would work, but is not ideal.  Some of the advanced features of mdaemon will need to be "what if'ed" to see if they will work as designed (e.g. backscatter protection, greylisting).  The chink in the armour could well be the ownership and broadcasting of Nameserver info.  The "virtual site setup" that manages nameservers is surely the "device that sits between 2 critical items"?
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by:moorhouselondon
ID: 20316288
About 123-reg:  My client had two problems which occurred simultaneously: 123-reg going down and the power going down.  What is the probability of that happening?    It took a while to realize that we had two problems rather than just the one.
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