Among the biggest concerns for permission email marketers today are email bounces, spam filters and blacklists - all of which affect email deliverability.
ISPs have been forced to employ various email blocking and filtering techniques. As a result, a spam filter could bounce your legitimate, permission-based email back to you, or your mail server might be flagged as a potential spam source. In either case, your messages won't make it through to the intended recipient.
The number-one reason permission-based email gets reported as spam is because recipients don't immediately recognize the message as something they asked for. Use a name subscribers will instantly recognize in the From field -- either your business name or your own name. Make sure your subject line identifies you as well. If you send a weekly newsletter, use a consistent name for that newsletter in the first part of your subject line.
If you're sending out email campaigns more than once a week, you need to have a very good reason for it
Set the expectation for how often you'll be emailing subscribers when they sign up for your mailing list. Something such as "Get our monthly newsletter along with program updates" would do it effectively.
Don't email subscribers every day. Annoyed recipients may simply unsubscribe. Angry ones are more apt to hit the "spam" button.
Relevancy: Send subscribers what they signed up for
What did you promise subscribers when they signed up for your permission-based email list? They're expecting content that's valuable and relevant to what they want and need. If people think they're signing up for one thing, and you send them something else -- they might get frustrated and report your email as spam.
You can even remind them of where/how they signed up by using a permission reminder at the top of each message.