Gmail uses many different references to determine inbox placement as well as delivery of your messages. Below are the top 10 email deliverability best practices you should follow when sending to Gmail as well as five bonus best practices regarding the Promotions vs. the Primary Inbox Tabs.

Opt-in. Gmail strongly suggests double opt-in or confirmed opt-in when possible. However, single opt-in is a must. SparkPost policy prohibits sending unsolicited messages.
Engagement. The most important thing to remember is to send messages to subscribers that are engaged with your brand. They are opening, reading, clicking and interacting with your brand. Interacting may mean purchasing or even getting involved with the discussion depending on your business model.
Overall list hygiene. Do not continue to send to email addresses that no longer exist or hard bounce (SparkPost suppresses hard bounces). Do not continue to send to subscribers that have not opened or clicked in a reasonable time. This length of time really depends on your business model. If you send daily or several times a week you should not continue to send to subscribers that have not opened or clicked in 6 months to a year with the same cadence as subscribers who have.
Monitor blacklistings. Gmail does use 3rd party blacklists (which ones are unknown) to determine inbox placement.
Avoid URL shorteners. Gmail will block most of them if used in bulk mailings, especially
Use the unsubscribe header. Make it easy for subscribers to unsubscribe from your message! Spam complaints are not shared back to you through feedback loops like other ISPs. Therefore it is crucial that your subscribers unsubscribe rather than reporting as spam. SparkPost deploys the list-unsubscribe header and suppresses unsubscribes.
Avoid affiliate marketing. Gmail states you should avoid affiliate marketing as a tactic. It is also against SparkPost policy to send affiliate marketing through our system.
Authenticate. Authenticate with both SPF and DKIM.
Subdomains. Use different subdomains that well define your different email streams. (Example:;; Be consistent. Don’t add too many as you want to be able to develop a reputation for each subdomain.
Warm up Domains just like you do IPs. If you add a new domain or subdomain do a traditional warm up to avoid bulking or blocks.
Gmail Warm up Volumes. Week 1 send 20,000 and double week over week.
Engagement. Send to your most engaged subscribers 1st then add lesser-engaged subscribers as your lists grows week over week.

Promotions vs Primary Inbox Tabs

Per-user filtering. Remember that just because some subscriber messages may be in the promotions tab does not mean that all subscriber messages are in the promotions tab. Filtering is done on the individual subscriber level not bulk sender level.
HTML to Text Balance. Keep the balance of HTML to Text similar.
Encourage Interaction. Subscriber awareness is important. Train your subscribers to expect the message and move the message into the Primary inbox. The messages should start going to the Primary inbox after a few moves.
Don’t send a promotion. When the above fails and you need a message to get into the inbox design your message to NOT look like a promotion.Personalize your messages. Include the reader’s first name in your message to Gmail subscribers.Lose the images. Gmail sees images as a sign of a promotion or spam message. You will in crease your readership by not having pictures.Letter format. Design the Gmail template to look more personal and natural like an email.Limit call-to-actions. The best way to keep from looking like a promotion is to have 1 link and not multiple upsells or RSS Feeds. Keep it short and simple!
Appreciate the promotions tab. When it comes down to it, if a subscriber wants your message in the primary tab they can move it there and will receive it there going forward. However, Gmail’s tabs are not new and subscribers know how they work and often go to the tab for promotions they are interested in.

Gmail rules look to be a little more relaxed once the introduction of the different folders. It is not like the scary wasteland of lost messages called the SPAM folder. If you have an interesting subject line and a brand that your subscribers want to engage with, the promotions tab will still get you opens and clicks.
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