Years ago, the e-mail delivery chain had just a few links. You loaded your e-mail and hit "send." After a couple handoffs, the message arrived in your recipient's inbox the way you sent it.

Today, that chain has many more links. Some block your e-mail, others help it along. Deliverability has become a big issue for many e-mail senders. It even spawned this column.  Here's how the delivery chain has lengthened over the years, along with the trouble each new link can cause...

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