Sending any form of email campaign, newsletter or autoresponder will always be subject to triggering spam filters. There are ways to improve your emails so they don't get accidentally marked as spam both by spam filters and your readers.
Here are some articles our developers have written to help improve your email deliverability and to reduce your emails being flagged as spam or blacklisted:
Improve your email delivery rates: http://www.interspire.com/content/articles/52/1/Improve-Your-Email-Delivery-Rates
Avoiding the Spam Filters and Other Email Marketing Tips: http://www.interspire.com/content/articles/6/1/Avoiding-the-Spam-Filters-and-Other-Email-Marketing-Tips
15 Email-Marketing Best Practices: http://www.interspire.com/content/articles/2/1/15-Email-Marketing-Best-Practices

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