Do you have subscribers claiming that they are receiving blank emails from you? Are these subscribers using email addresses, email addresses, or email addresses? If so, this could actually be caused by an old bug with Yahoo’s “Classic” web email interface.
Basically, the problem only occurs when users are using old Yahoo, AT&T, or SBCglobal email addresses, which are still set to the “Mail Classic” layout view. This ends up being a very small percentage of users, but it does still occur from time to time. Our software is not actually sending blank emails, but the “Mail Classic” web mail client is adding a CSS property called “visibility: hidden;” around the entire email. This CSS property is making your entire message invisible.
The original “Mail Classic” view will hide your entire message (using “visibility: hidden;”) until all images in the message have been loaded, and then it will remove the “visibility: hidden;” property and display the entire message at once. The point of this is to make the message loading process a more smooth transition. However, if you have a broken image tag in your message, or if an image in your message fails to be loaded for any reason, it is possible that the “visibility: hidden;” CSS attribute may never be removed, thus causing your entire message to remain hidden/blank.
If you find that any of your subscribers who are using Yahoo/AT&T/SBCglobal email addresses are reporting that they are receiving blank emails, you can:

  1. Check your message to make sure there are no broken image tags or broken image links within your HTML code, or
  2. Ask the subscriber to click “Printable View,” which will show them the entire message, or
  3. Ask the subscriber to try switching from the outdated “Mail Classic” layout to the new layout (they can click “try the new Mail” to do this), which is the only true permanent fix.

Again, this is not an issue that we have any control over, unfortunately — it is a bug in the old “Mail Classic” interface for Yahoo/AT&T/SBCglobal users. Though there are only a small percentage of Yahoo users still using the old web interface, and this problem will only occur when there is a problem loading images, the issue might still pop up occasionally with some of your subscribers. Switching to the new web layout will resolve the issue permanently.