Every web application sends emails: registration, forgot password, reminders, etc. How do you make sure that these emails get into your user’s Inbox? There are 2 ways: "free" do-it-yourself approach is described at the end of this post. The easier, but not free, approach uses an SMTP Relay Provider.

These providers usually have relationships with major web-based email solutions (gmail, yahoo, hotmail, etc) and also follow the latest standards and best practices for making sure that your email is delivered. Some of the things these companies do is outlined in the DYI portion.

SMTP Relays should not be confused with "email marketing" offerings. Email marketing offerings usually specialize in List Management, opt-in/opt-out, tracking, etc. Most of SMTP Relays do not offer these features.

Here is a list of the providers that I found while researching this:

SMTP Relay Providers

www.unifiedemail.net

• We implemented this for a customer (their choice) and had no issues with it. Implementation was easy, pricing seems reasonable.
• Site is a bit sparse on information but customer reported that phone support was prompt and helpful
• You can find pricing here, but to give an example: with 5K daily limit/75K monthly limit you will pay $99.95/month

www.sailthru.com

• NYC-based, recommended by a few people on nextNY list
• Pricing: $6 per thousand of emails, $60 monthly minimum, discounts after 500K
• Seems to offer a few additional features on top of regular relay: "Triggermail — Our flagship service monitors delivery of transactional email into the user Inbox. If it gets sent we’ll tell you when it was delivered and what happened when it was opened."

www.authsmtp.com

• Another one that was recommended by a few people on nextNY list
• When looking at pricing keep in mind that listed limits are monthly, but the price is yearly. Here are monthly prices to make it easier to compare to other services:
  • $2/month for 1K emails/month
  • $14/month for 10K emails/month
  • $134/month for 100K emails/month
  • $667/month for 500K emails/month
  • goes up from there

www.socketlabs.com/od

• Pricing:
  • $79/month for 25K emails/month
  • $249/month for 100K emails/month
  • $449/month for 500K emails/month
• You do not get a dedicated ip with the first 2 plans. Not sure how big of an issue as long as SocketLabs keeps their IP range clean

www.smtp2go.com

• Looks like they target consumers as their highest plan allows for up to 300 emails a day
• They offer "corporate" product (https://smtpcorp.com/signup/), but it still doesn’t look like an STMP Relay product

www.port25.com

• Pricing is not listed on the site – you have to contact them. Hard to believe that companies still play "personalized quote" game

DYI Approach

Very good post on this topic can be found here: How to ensure your email gets delivered

This covers email marketing techniques, but applies to this discussion as well: How can I prevent my emails being marked as spam or from being blacklisted

Note: This checklist below is a modified version of a post from Oct 2007 by Tobin Schwaiger-Hastanan on Business of Software List.

First steps:

• Make sure your mail host is a valid A record
• Make sure your MX record is set to the full host name of your mail host (which is set up as a A record)
• Make sure you can do a reverse lookup of your mail hosts IP address.  (This will be important for setting up SPF/Sender ID records)
• Set up SPF/SenderID information as a TXT record. (www.zytrax.com/books/dns/ch9/spf.html)

Once above is configured

• Verify DNS/MX records using http://www.dnsstuff.com/. Make sure there are no warnings or errors before contacting support for any of the email services. Yahoo has a policy of not reviewing changes for 6 months after the last request is made
• Test your emails with Spam Assassin.  Send yourself an email from your web application and copy the raw message (including headers) to a text file and run it against spam assassin’s command line test. The lower the score the better.  A score of 5 or more means that your email will most likely get filtered out by any spam filter.  I’ve also been told that anything 3 or higher is bad.
• Once you’ve tested out your emails in spam assassin, try testing it out across other services.  I initially was using Email Reach (www.emailreach.com). I think it’s a great service, but it’s still a young/small company. So if you find issues/bugs with their product, you will need to have patience with their customer service.  It’s a cheap product for what it does.  It will test delivery of your email to a large list of email providers, ISPs, and even email clients.

Tips

• If you are sending plain text emails, make sure you have the charset in the Content-Type header set to ISO-8859-1. When I changed the charset to ISO-8859-1, gmail was no longer delivering my emails to the spam folder.  However hotmail and yahoo still were.
• Yahoo! Mail allows you to view the headers of incoming emails.  You can see items they’ve added to the header.  Review them
• Visit http://postmaster.hotmail.com and review their policies and troubleshooting guides. If you adhere to their rules, try to contact them
• Implement DomainKeys on your mail server.  This is basically a crypto key that is stored in a DNS TXT record, and some work done on your mail server to get it to sign outgoing mail.