• by Jack Loechner , Staff Writer @mp_research, June 7, 2007

Multiple Images and Unidentifiable "From" Names Trigger Spam Filters

The primary findings of the Lyris EmailAdvisor ISP Deliverability Report Card for Q1 2007, are that message content is NOT the key reason ISPs filter legitimate email marketing messages. And, a majority of the largest US-based ISPs have the lowest rates of delivering email to the inbox.

Testing the content of more than 1,705 unique emails with EmailAdvisor's content scoring tool, based on the content scoring rules of the Spam Assassin open source project (a Bayesian filter that applies point values to multiple possible spam-related signatures and sums to an aggregated point total for decision making purposes), the emails had an average content point score of 1.04 well below the filter's generally accepted spam identification level of 3.0 or higher.

The two frequently triggered Spam Assassin rules that generated content filter point scores of significance were:

• Heavy use of images, which can increase spam scores up to a full point and render poorly in email clients with image blocking enabled
• Sending messages with a "From Name" composed of numbers or symbols rather than an actual name

Of the 25 U.S. ISPs tracked in the study, several leading providers rank near the top of the list with the highest rates of delivery to the junk folder rather than to the inbox. These include:

• Gmail (3rd with 28 percent)
• Yahoo! (4th with 19 percent)
• Hotmail (6th with 16 percent)

Noticeably absent from the top ten ISPs with the worst inbox delivery is AOL, which ranked 14th on the list with a junk delivery rate of only 2.33 percent.

For the study's top-ten-ranked U.S. ISPs, gross deliverability was more than 90 percent in all cases, with average deliverability of 83.8 percent across the sample. CompuServe had the highest rate of inbox delivery at 88 percent, with the remainder of the top-ten-ranked ISPs achieving delivery rates of more than 81 percent in all cases.

Of the 25 U.S. ISPs reported on, several of the leading consumer ISPs rank among the domains with highest rates of email delivery to junk/bulk folders rather than to the inbox. These ISPs include Gmail (3rd), Yahoo (4th), and Hotmail (6th). A top ISP with much better delivery was AOL, which ranked 14th on the list with only 2.33% of email being delivered to the junk/bulk folders. While average gross deliverability is around 83.8% for permission-based marketing, all of the top-ten ISPs delivered more than 90% of email received. The lowest delivery rate was seen at Lycos, where only 41.7% of email was received-this is almost 29% lower than the next-worst ISP, AT&T, which delivered 70.8% of all messages.

While marketers are struggling to improve the overall delivery of their emails, inbox delivery is still the key challenge. CompuServe which had the highest inbox delivery rate still only achieved 88% inbox delivery. The other top-ten ISPs all had inbox placements in the 80% range. Hotmail scored third from the bottom with only 58.4% of delivered messages reaching the inbox.

Top Ten US Domains by Gross Deliverability
Rank	ISP Name	Percent Delivered
1	IWon	96.97%
2	Yahoo!	94.80
3	Google Mail	94.65
4	XO Concentric	94.27
5	USA	93.59
6	SBC Global	92.24
7	PeoplePC	91.28
8	Earthlink	91.27
9	Bell South	90.71
10	AOL	90.06
	AVG	83.88
Source: Lyris Technologies, May 2007

 

Top Ten US Domains by Inbox Deliverabilty
Rank	ISP Name	Percent Inbox
1	Compuserve	88.09%
2	AOL	87.73
3	Juno	87.07
4	NetZero	86.72
5	Earthlink	85.75
6	PeoplePC	84.60
7	Mail.com	84.05
8	IWon	83.86
9	USA	83.26
10	Mac	81.76
	AVG	74.57
Source: Lyris Technologies, May 2007

  

US Domains with Highest Delivery to Junk/Bulk Folder
Rank	ISP Name	Percent Junk/Bulk
1	XO Concentric	48.34%
2	Bell South	28.29
3	Google Mail	27.75
4	Yahoo!	18.61
5	SBC Global	18.22
6	Hotmail	16.16
7	MSN Network	15.83
8	IWon	13.11
9	USA	10.33
10	Verizon	7.31
	AVG	13.14
Source: Lyris Technologies, May 2007

The average deliverability at European based ISPs ranks higher than their U.S. counterparts by almost 7 percentage points and slightly higher than Canadian and Australian ISPs by 0.5 and 2.5 percentage points respectively.
The average inbox delivery scores were also higher for European-based ISPs, with 82.4% of email being routed correctly to the inbox, compared to only 74.5% for U.S. based ISPs. And, European ISPs had the lowest percentage of junk/bulk folder delivery at only 7.6%, compared to the U.S. at 13.1% 

For the complete PDF report, please visit Lyris here.