“Most email marketers do not view soft bounces as being a major cause for concern,” says Dela Quist in the UK DMA Email Marketing Council newsletter, “so rarely, if ever, have any specific strategies been in place for dealing with them.”

According to Quist, this erroneous belief is based on outdated assumptions—namely, that soft bounces are caused by busy servers or full inboxes. The catch: Neither of these is a pressing issue in 2009. “Gmail currently offers 7GB of storage!” Quist says. “I don’t know anyone who has exceeded their Gmail—or for that matter, [their] Yahoo or Hotmail storage limit—and even if there are such people, they are hardly representative of the average consumer.”

Because of this, concludes Quist, a soft bounce is most likely caused by temporary ISP blocking, an action often triggered by:

  • A lack of authentication
  • A poor IP reputation
  • Fluctuations in volume
  • Spam complaints

Whatever the reason, it probably isn’t good, but can be addressed in coordination with your ESP.

Heads up! Handle soft bounces with the same attention you give to hard ones. They might not be as harmless as you think: they can, in fact, be a sign of a far more serious situation.

Source: UK DMA.