What is the best way to overcome Gmail spam filters in email marketing?

make sure the 'to' em...

While there are general rules of thumb as highlighted above to get good delivery rates Gmail has a couple of things to be aware of. They like DKIM http://en.wikipedia.org/wiki/DomainKeys_Identified_Mail, a lot! Other ISP's do give you better placement if you have DKIM but without it Gmail delivery to inbox is tough. They also like 'list unsubscribe' http://www.list-unsubscribe.com/this gives the user the ability to unsubscribe from within the interface of Gmail as opposed to within the email. They also place more value than any other ISP on recipient activity so encouraging your subscribers to add you to contacts and/or pull you out of the spam filter has a big impact. There is also some evidence that simply mentioning gmail in the subject gets better delivery rates!

For Gmail, the sender reputation and recipient engagement play a big role when it comes to deciding where to put the inbound email. Gmail calculates reputation based on the user's actions on the email. Every time the email gets a certain amount of spam markings from Gmail users, the reputation of the sender goes down.And as they get non-spam markings that is when users move emails from the Junk folder to the Inbox, the sender gets some positive reputation. The reputation then plays a significant role for how Gmail treats the email.Engagement is seen as the sum of total user's actions upon the email. Gmail tracks explicit user's actions (marking email as spam, replying to the email, moving it to the Junk folder etc.), and these explicit actions have a direct relation to how Gmail classifies the email for the given user.If the subscriber opens emails from you on a consistent basis, that shows engagement and favors Inbox placement for the current and next email campaigns.But if the subscriber leaves the emails unread, deletes them without opening or moves them to spam, then Gmail will penalize the sender because the subscribers don’t appear to be engaged with the emails.So, the main tip is to try to keep the users as engaged as possible. Here you can read about more tips how to deliver emails to the Gmail's Primary tab http://glockapps.com/blog/improve-delivery-to-gmail-inbox/

As a benchmark, email deliverability should be over 98%. There are a number of key factors that ensure this: Make sure the email list is clean and quality tested. There are a number of companies that will do this for you. Avoid the use of 'spammy' wording in your title and subject lines e.g 'free'. Get a good balance of images and HTML text. An email made up of only one or the other can be picked up by spam filters. You can get white listed to avoid being caught in spam filters all together. Don't send emails too frequently, this can lead to customers sending your emails to junk. Make the unsubscribe option clear. It is far better for a customer to unsubscribe, than for them to send your emails to junk.  Hope this helps. CB.

Test your subject lines here first: http://www.localnews.biz/subjectLine/ValidateSubjectLine.asp