Wishing to send an email to about 20,000 recipients.

Our own SMTP server used for transactional emails I believe is well trusted, we've not heard of deliverability problems, mails go to gmail/yahoo fine. DKIM, SPF, DomainKeys all set up, etc.

What program should we use to send the email? Would people recommend bulk email software like Sendblaster? Would this handle unsubscribes, etc?

Send via SMTP server or connect direct to theirs? Know some of this software can connect directly to the the recipients SMTP server. Is this advisable or is sending via a trusted SMTP server better?

Use our own SMTP server vs provider like SendGrid/Critsend? Presume if we were using bulk email software we'd have to connect to a SMTP service. Are we best sending using one of these services or our own server? My thinking is the bulk sender providers may not have sent emails before to the people we're sending to and as such perhaps our server has better reputation?

If our SMTP server, what software (Windows)? Currently using SmarterMail, is this up to it or should

Update: https://www.senderscore.org/ reports our mail server IP with a score of 99, low delivery risk and very low volume.

Any opinions?

Edit: thanks for the answers so far. Providers like MailChimp are just too expensive for one off emails. Plus they don't seem to like bought lists - in the UK this is fine if the data is collected lawfully under the List Warranty Register - http://www.dma.org.uk/information/ind-listintro.asp

3 Answers 3


I would advice you to use a service specialized in sending bulk e-mail, like for example Silverpop or Mailchimp. The main reason for this is that their antispam whitelisting. You don't want your normal mail server/web server getting in a blacklist because some of your users didn't like the message.

You probably also don't want to send only one message once, and this services offer list managing, with unsubscribes, templates, segmenting A/B testing...

Another option is to look for CRM providers with mailing services included, but that is a more expensive option with many features that you would probably never use.

  • Like Osvaldo mentioned, one of the great things about a provider like MailChimp is that they can give you all sorts of feedback regarding your campaign. Analytics are great to tweak your campaign for better click throughs and opens.
    – JonLim
    Commented Apr 8, 2011 at 19:49
  • Unfortunately I can't use Mailchimp or similar as they don't like bought lists. However the list we're using is from the UK Office of Public Sector Information which as far as I'm aware is fully legal as its open information.
    – Marcus
    Commented Apr 13, 2011 at 20:44

Bear in mind a minority of recipients will helpfully unsubscribe by using the "report spam" option rather than the unsubscribe link you provide. This means you have a chance of being temporarily blacklisted somewhere, even when you did nothing wrong.

So, as Osvaldo says, use one of the known providers who already have processes and whitelisting in place for this, like Mailchimp or Constant Contact. They've got pretty much all you need in terms of click tracking, open statistics and the like.

Why reinvent the wheel and risk taking your mail off the web in the process?

  • Thanks. I'm not so sure I'm worried about people clicking Report Spam. I dont think any emails are going to free email providers - everything is going to corporate addresses. Also, no US places seem to like using purchased lists. Things are a little different in the UK though if bought from a provider registered with the List Warranty Register - dma.org.uk/information/ind-listintro.asp
    – Marcus
    Commented Apr 9, 2011 at 11:56
  • Hm, I took it as a mixed list as you mentioned yahoo etc in the question. I'm not sure we trust incoming email here in the UK any more though - too many break the rules.
    – Matt
    Commented Apr 9, 2011 at 15:45
  • Yeah I accept I wasn't too clear in the question with mentioning free providers. I guess most enterprise mail servers will use blacklists/spamassassin/postini services to filter spam. Exception of the above are enterprise people on Google Apps, however currently our mail to Gmail is all fine.
    – Marcus
    Commented Apr 9, 2011 at 15:57

There are a few issues at play here...

  1. Bulk emailing services specialise in that very specific, and extremely tricky field. It can be extremely difficult to ensure your emails will go through and won't result in domain level spam blocking when you roll your own, especially if you don't have much experience with email marketing, or bulk email sending.
  2. Bulk emailing services have designed their architecture specifically to handle sending of huge numbers of emails in a relatively short period of time without tying up too many system resources. Most general SMTP servers are not designed in this manner, rather they have been built into a full blown email server environment and are more designed to send a smaller number of emails less frequently given their design as sending emails made by humans, not by hitting copy and paste a huge number of times.
  3. Bulk email providers warm up their servers over the course of many months, sending more and more emails from them before they finally hit the point that they are sending huge numbers of emails from them. If you start doing this from a "cold" server you could easily find yourself getting your serer and/or domain and/or IP addresses put onto a blacklist as a sudden sharp spike in email traffic from a particular source is one signal used in assessing the likelihood that an email source is sending spam.

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