Image Blocking Issue in Most Known ISPs & Email Clients

Most commercial e-mail messages are sent in HTML or a multipart format and include images: logos, header images, product pictures or sender’s photos. Many all e-mail marketers host images on a web server and specify the path to them in the message. To load the images, a call is made back to the hosting server. Many ISPs and some e-mail clients block this call. This is done primarily for security reasons. Using image blocking capabilities people can prohibit adult images from loading and prevent spammers from knowing if the message was opened.

The table below shows how major ISP and email clients handle images in received messages.

 
Image handling capabilities
AOL v6.0-9.0
Gmail
Hotmail
Yahoo
Outlook
2000-XP
Outlook
2003
Outlook
Express
with SP2
Outlook Express w/o SP2
External images are blocked by default
  

X

X

X

  

X

User controls image blocking settings
 

X

      
User clicks link to show images
   

X

X

  

n/a

Images are enabled if the sender is on the recipient’s whitelist/address book
 

X

 

X

    
Images are auto-enabled if the sender is on the IS whitelist
 

n/a

 

X

n/a

n/a

n/a

n/a

ALT tags are displayed when images are disabled

X

 

X

X

X

X

X

n/a

Preview window enabled

X

X

X

X

    
 

Giving the fact that not all the email clients automatically load images when the email is received, you should tailor you email newsletter for all possible environments. If the images are important, consider including a link to a web version of your newsletter or simply give a link to the website where people can view the images and read more about your products or services.

 

 

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