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We currently have our own in-house email marketing software for our newsletters, and were using SQL server's SMTP agent to send emails through our local SMTP server (IIS) and then onto our ISP's SMTP Relay.

The SQL Server was involved because the email addresses of the recipients are stored in the database and because it takes the content of the newsletters and we use .net to construct the emails for delivery.

About 1 month ago our ISP got the impression we were sending spam (our email volume is approx 20k a day) and blocked the SMTP relay. After much debate with them, we've given up with them, but realised that they came to this conclusion due to the high volume of NDRs.

We've solved the problem with the NDRs but going back to the ISP SMTP relay isnt currently an option.

Using IIS as a direct SMTP server is not ideal because we cant implement systems that will help us to deal with bypassing spam filters since we need to implement DKIM and SPF and its not so easy on IIS.

We tried using our shared hosting accounts with just standard SMTP hosting to send out our emails from the SQL server but the email limit is set to 300/hr which isnt high enough, and currently using something like SendGrid is just too costly at this volume since we dont profit from the newsletters.

While i have previous experience with Exchange 2003 and 2007 i just find the maintenance and hardware requirements to be quite involved at times and am looking for a minimal but flexible and capable solution for an SMTP that can support DKIM and SPF.

I have been considering something like QPSMTPD or the Node.js port; Haraka.

Does anyone here have any experience with the above and how quick and easy are either to implement, maintain and extend?

What about DKIM and SPF support?

What about dealing with such a high volume and required speed?

Am i likely still to come across spam filtering issues and problems with my ISP?

Does anyone have any insight they can share on this matter?

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You're asking a LOT of questions in one. To improve on your question, I think you should be asking: "What is the best way to send out a high volume email newsletter and manage the NDRs/unsubscribes appropriately?" –  MikeyB Oct 27 '11 at 0:05

3 Answers 3

Every recent mail server is capable of doing the job with that minimal requirements you provide. You are sending only 800 mails per hour. This can be done in 5 minutes without pain.

So check the server that fits your requirements. Any of Sendmail, Courier, Qmail, Exim or (my favorite) Postfix can do what you want. Without any problem.


But I would not jump on the train to use your "recommended" solutions. They are exotic mail servers whereas the mentioned above have a history of over 10 years of development. Sendmail is even 18 years old and it's ancestor even 30 years. So stick with the "good old" ones.

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I send 500 mails in a minute with postfix on a tiny virtual machine. There really is no need to go crazy here. –  Michael Hampton Sep 5 '14 at 17:30

our ISP got the impression we were sending spam

Not a big surprise. Managing an email server is not a trivial task, configuring/managing an email server for bulk emailing requires a lot more skill (SPF/DKIM is just the start of the story).

You're email volumes are large enough for you to start running into problems even if you run your own server - but probably not large enough for it to be financially viable to acquire and maintain the level of knowledge to operate the service yourself. I'd strongly recommend looking for a reputable bulk email provider (sorry, can't give you any specific leads).

If you do want to go down the route of running your own server, I would recommend steering clear of MSExchange - IME its expensive, difficult to configure/maintain and less reliable than most of the other mainstream MTAs.

Obvious candidates would be sendmail (very configurable - but requires a through understanding) or postfix (much easier to configure, and the lower throughput is unlikely to be an issue). You definitely want something with milter support. Based on previous experience, Exim and Qmail lag a long way behind in terms of stability.

If you really must run it on MSWindows, have a look at iMail - but AFAIK it does not support sophisticated queue management.

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Testing Haraka for a while now and I would recommend nothing else but this. Haraka is actually a framework where everything is a module. Very easy to use, source code is readable, available on github, no magic. DKIM/SPF support included over plugins. I don't have speed tests for now but so far I don't have any serious issues. I wrote a working production app on top of it for a client in less then a week.

Btw... I used Postfix and Exim4 in the past. I have good memories with Postfix and bad with Exim4 (bugs). Anyway, I'm not a fen of the previous century stuff and playing with that-like configuration syntax just doesn't fit into my workflow any more :).

I hope it helps.

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