There are two major factors to consider when you find that your message is going to the junk, bulk, or SPAM folders.
The Reputation of the Sender of Your Messages
As a hosted solution, AWeber's customers' messages are sent via our mail servers, something that the ISPs (e.g. Yahoo! Mail, Hotmail, etc.) review when deciding whether to accept or reject a message.
We've been in the business of sending only requested messages since 1998, following the strict industry standards required for excellent deliverability.
The Content of Your Messages
Once your messages get through the door, ISPs will subject them to content filters to help determine whether to put messages into an inbox or another folder.
Some of these are commonly used, such as the SpamAssassin filter, for which we provide a content analyzer so that customers may test their messages.
Still, others are proprietary and to avoid the adaptation of spammers methods to get their junk through, ISPs won't release information on them.
What Can I Do to Avoid Deliverability Issues?
More on effective image usage on our blog