Are Your Subscribers Getting Your Newsletters?

I've been gathering delivery data on the four email broadcasting services I reviewed previously (FeedBurner, Zookoda, Squeet, and FeedBlitz). In my first test, I setup Zookoda and FeedBurner with my EDA Geek test mailing list (about 30 posts a week). I setup Squeet with EDA Blog, which has about five posts a week. Lastly, I setup FeedBlitz with this site, iZachy (about five posts a week during the test period). If I had to do it again, I would have set up all the services with the same site, but I setup the newsletter via FeedBurner. With the FeedBurner interface, you have to disable FeedBlitz and Squeet if you want to use the FeedBurner email service. In hindsight, I should have setup the newsletter directly from the FeedBlitz and Squeet sites.

With each email service I tested, I added my Outlook, Gmail, Yahoo, and Hotmail accounts to the mailing list. When you read the rest of this article, keep in mind that my tests are far from being scientific. I could and should have done a better job in keeping the factors influencing the outcome consistent with each service. Nevertheless, I think the results are interesting.

emails delivered

As you can see from the above chart, 94% of the newsletters arrived in my inbox from FeedBlitz, but only 60% from Zookoda. I was very surprised by the 60% figure. The results could have been better or even worst depending on the ISP you use for your Outlook emails. The first 21 newsletters to my Outlook account from Zookoda were stuck in the spam filter on the server. They never made it to the inbox on my computer. I had to log into the email server to retrieve them. This is not something most subscribers will do to get their free newsletters. After I switched ISP (for unrelated reasons), I got the next ten newsletters in my Outlook inbox without any problems. It appears some ISPs (well at least one ISP) have filters in place that can block Zookoda newsletters from your inbox.

Why Zookoda Gets Blocked

I have three theories on why Zookoda emails are more likely to be blocked than the other three services I tested. First, the "from" field does not match the mail server info in the email header. The "from" field in my Zookoda newsletters is However, the email header indicates the newsletters are actually being sent from, the commercial email service owned by Zookoda's parent company. Isn't this a common technique of spammers — sending emails with one domain listed in the "from" field when the emails are actually being sent from a completely different domain?

The "from" fields for the other email services are:,, and on behalf of The last one is for FeedBurner, which is using to send out newsletters.

My second theory involves the honor system that is used when importing "opt-in" email lists to Zookoda. Having run the email marketing program at a major corporation, I can tell you that the honor system does not usually work. Marketing managers always tell me their email lists are opt-in's. A lot of these lists were not opt-in's and they generated a lot of opt-outs, bounces, and "I love you" phone calls from the Spam Fan Club.

The other three email services I reviewed do not rely on just the honor system: Squeet must approve your list before they allow you to import your list to their service, FeedBurner does not let you import lists directly (their team does the import), and FeedBlitz sends out notification emails to addresses on your import list. Most publishers who use Zookoda are honest, but the honor system does make it easier for spammers. The more spam generated via Zookoda (Quivamail), the more likely Zookoda will get flagged.

My third theory has to do with the subscription process. Both FeedBurner and FeedBlitz ask a question to verify you are human before they send verification emails to subscribers. On the other hand, Zookoda does not have an image verification step to screen out bots. As a subscriber, I hate the image verification step. However, the extra step makes sense if you don't want your service flagged by email servers. Consider what would happen if a bot submits a bogus email address several thousand times. Zookoda would send out verification emails thousands of time to xyz company and they would all bounce. Don't you think the email admin at XYZ company would notice all the bounces from Zookoda and start flagging emails from Zookoda? (Note: Squeet does not have an image verification step, but subscribers have to fill out an addition form to subscribe.)

Yahoo and Hotmail are Playing Games

In my second test, I switched the "from" field in Zookoda from something@yahoo to something@mydomain. I used my Yahoo account to create an account with Zookoda and didn't realize it would be used as the default "from" address. After the switch, more emails arrived in Hotmail (increased from 35% to 68%). It appears Hotmail was flagging Yahoo addresses. On the other hand, fewer emails arrived in Yahoo (dropped to 68% from 91%). Yahoo was more likely to deliver emails from other Yahoo email users. That explains why I get a lot of spam in my Yahoo account from other Yahoo addresses.

who's the email from matters

Gmail Lets in Everything

It appears Google lets just about everything in. The delivered rate was anywhere from 92% to 100%. It doesn't matter which service you use or what you have in your "from" address, Google will let it in. I found this a bit odd because I get very little spam in my Gmail account. If Google lets everything in, shouldn't my Gmail account be flooded with spam? I'm not sure if Google has a great spam filter or if it's because I have not had my Gmail account as long as my Yahoo and Hotmail accounts.

What Does All this Mean?

If most of your subscribers are using Gmail, it doesn't matter which service you use. They will get your newsletters. If reliability is critical (ie – paid subscription), FeedBlitz offers the highest delivered rate. If you are using Zookoda to send emails to Yahoo or Hotmail accounts, you can increase the deliverables by separating your list to separate Yahoo and Hotmail address lists and setting the "from" field to match the list. If your subscribers are using a desktop email client like Outlook and you love all the features of Zookoda, consider creating a second list with another service. If people complain that they are not receiving your newsletter, remove them from Zookoda and add them to the second list. You can also be proactive by contacting subscribers or posting a note on your site.

Below are the delivered stats for the four email broadcasting services I tested.


percentage Outlook Gmail Yahoo Hotmail Total
inbox 79% 92% 92% 88% 87%
spam filter 7% 0% 0% 4% 3%
missing 14% 8% 8% 8% 10%
Total 100% 100% 100% 100% 100%

raw count Outlook Gmail Yahoo Hotmail Total
inbox 22 22 22 21 87
spam filter 2 0 0 1 3
missing 4 2 2 2 10
Total 28 24 24 24 100


percentage Outlook Gmail Yahoo Hotmail Total
inbox 78% 94% 94% 89% 89%
spam filter 17% 0% 0% 0% 4%
missing 6% 6% 6% 11% 7%
Total 100% 100% 100% 100% 100%

raw count Outlook Gmail Yahoo Hotmail Total
inbox 14 17 17 16 64
spam filter 3 0 0 0 3
missing 1 1 1 2 5
Total 18 18 18 18 72


percentage Outlook Gmail Yahoo Hotmail Total
inbox 95% 93% 93% 93% 94%
spam filter 0% 0% 0% 0% 0%
missing 5% 7% 7% 7% 6%
Total 100% 100% 100% 100% 100%

raw count Outlook Gmail Yahoo Hotmail Total
inbox 19 13 14 14 60
spam filter 0 0 0 0 0
missing 1 1 1 1 4
Total 20 14 15 15 64

Zookoda (from = something@yahoo)

percentage Outlook Gmail Yahoo Hotmail Total
inbox 32% 100% 91% 35% 60%
spam filter 68% 0% 0% 10% 22%
missing 0% 0% 9% 55% 18%
Total 100% 100% 100% 100% 100%

raw count Outlook Gmail Yahoo Hotmail Total
inbox 10 23 21 11 65
spam filter 21 0 0 3 24
missing 0 0 2 17 19
Total 31 23 23 31 108

Zookoda (from = something@mydomain)

percentage Outlook Gmail Yahoo Hotmail Total
inbox 74% 100% 68% 68% 77%
spam filter 0% 0% 0% 12% 3%
missing 26% 0% 32% 20% 20%
Total 100% 100% 100% 100% 100%

raw count Outlook Gmail Yahoo Hotmail Total
inbox 20 25 17 17 79
spam filter 0 0 0 3 3
missing 7 0 8 5 20
Total 27 25 25 25 102

9 thoughts on “Are Your Subscribers Getting Your Newsletters?

  1. excellent analysis. at the moment I use Feedburner, and am quite happy with it. I guess i'll give feedblitz a try based on your figures….

  2. That's why RSS is so cool: If you trust a Website you can subscribe to their feed and you will never get spam. The publisher benefits, because you really get ALL "mails" to your inbox.
    But since not everyone does know what RSS is, not talking about people who actually can receive RSS it will not be a replacement for newsletters in the near future I guess :/

Comments are closed.