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How to deliver into Gmail

Email deliverability today is driven by content and reputation filtering. While it would be great if there was a single algorithm that all of the mailbox providers used, there isn’t. Gmail,, and Yahoo! Mail all have their own unique spam filtering rules and services to help senders. Our field guide aims to help businesses overcome confusion from the different rules of deliverability, or those who are just strapped for time.


Unlike many of its large competitors, Gmail doesn’t provide feedback loops, whitelists, disclose use of public blacklists or
provide a lot of direction, tools or support for senders. Don’t worry about the lack of information Gmail provides. We’re here to help.
Gmail by the Numbers
Launched: 2004
Active Users as of 2012: 425 Million
U.S. mobile users using the Gmail app: 44.3%*
How many days prior to Gmail’s launch it took to design the Gmail logo: 1
Number of email addresses that can be created by adding a + symbol in front of the email address: ∞
The year Gmail purchased the domain from 2005
*(August 2013 U.S. Smartphone Subscriber Market Share - comScore, Inc)

How Gmail Filters Spam 

Gmail, like many major mailbox providers, primarily uses its community of users to determine whether email is spam or not.
Gmail considers the following user feedback important in their spam filtering decisions:
1. Report spam
2. Not spam
3. Messages Read
4. Messages Read and Deleted
5. Starred messages
6. Messages replied to
7. Inbox Activity
As with most spam filters, the content of the email headers, body and attachments are also scoured for keywords, images, HTML, URLs, malware and many other common components. Content is always tied and added to the overall spam filtering algorithm, but how much weight it carries usually depends on the reputation of the sender.
Sending History
Gmail temporarily blocks new IP addresses without a reputation for the first 2 – 24 hours, then delivers small amounts of mail to both the inbox and the spam folders to gauge subscriber perceptions. If complaints are too high, future emails will be delivered mostly to spam. If more people click on “not spam” during this period, this indicates that the mail is safe to be delivered to the inbox.
The number of active Gmail users may influence your reputation, and therefore your inbox placement. A look at top brands and the percent of their subscribers that are engaged – showing any activity regardless if its negative or positive – shows a strong correlation.
Chart: Brands with higher percentages of active users are more likely to receive inbox placement.
However, our research shows a correlation between spam filtering at Gmail and Spamhaus.
Enterprise Filters
As an aside, it’s important to understand that although Google owns both Gmail and Postini products, each service utilizes its own unique proprietary filtering technology. Google Postini Services is a B2B spam filtering solution used primarily by corporations to manage their enterprise mail. However, Google is switching current subscribers of Google Postini services to Google Apps by the end of 2013.
If you find your mail getting stuck in Google Postini Services’ spam filter, Google does provide a Message Analyzer that allows senders to examine the tags inserted into an email header to help decipher the reasons for the quarantine. You may find a hint of the issues with this tool but the only way to figure out how to get through this filter is to constantly test different email content.

Mail Infrastructure

When it comes to having a proper email set up, Gmail’s advises:
1. Consistently send from the same IP address(es)
2. Have valid rDNS for sending IP addresses pointing to your domain
3. Use the same “From:” domain based on the type of email
4. Authenticate sending domains with DKIM and SPF
More on Authentication
SPF and DKIM authentication should be implemented. Be sure that your From: domain matches the d= in your DKIM record. Senders using shared IPs at ESPs should sign DKIM with their own unique signing domain. For example, one should be signing mail with something like instead of If for some reason you are not authenticating then Gmail creates a “bestguess” record using a combination of record lookups to match your sending IP with your domain to authenticate your email.
Gmail does have thousands of hosted business domains that are using Google Apps.

Postmaster Services

1. Gmail Bulk Sender Guidelines
    Gmail advises the best way to reach the inbox is by complying with their Bulk Sender Guidelines:

• Publish an SPF record and sign with DKIM
• Get Permission
• Have an Unsubscribe link prominent
• “Not Spam” clicks – tells Gmail the messages are solicited
• Like with like – use different email address, domain, and IP for different types of mail, like promotional and transactional Senders can submit messages continually delivered to spam, despite following and exceeding best practices, for review on their Bulk Sender Contact Form.
2. Feedback Loop
Gmail does not offer a feedback loop service in the traditional sense. For senders using the list-unsubscribe header, whenever an email is marked as spam, the subscriber will be asked if they want to mark the email as spam and/or also unsubscribe from future mailings. To prevent abuse of this feature, the unsubscribe feature will only work for senders with good reputations in the Gmail network.
In enable this functionality, the following are required:
• The email messages have a list-unsubscribe header which points to an email address or an URL that a subscriber can easily unsubscribe
• Sending domains publish an SPF authentication record, sign outgoing email with DKIM, and pass at least one authentication protocol
• The sender has a good reputation within the Gmail system. Go to Gmail’s Bulk Sender Guidelines for more information, or verify your reputation at, where inbox placement at Gmail and one’s Sender Score are highly correlated.

What is list-unsubscribe?

Josh Baer (Chief Innovation Officer and founder of OtherInbox, a Return Path company), and his friend Grant Neufeld created the list-unsubscribe mechanism in 1998 while still in college. RFC 2369 details the technical specifications of the header, but the concept is simple – add a unsubscribe mechanism in the email header and email providers can offer better unsubscribe functionality than the link buried in the footer of most emails that are required by the United State’s federal law, CAN-SPAM, as well as other internaitonal laws regulating email and spam. Josh Baer also has a website devoted to list-unsubscribe that includes the specification and the participating mailbox providers that use it.
Unsubscribe Methods
Besides reporting email as spam, Gmail users can access the listunsubscribe functionality by showing message details.
Show Message Details
To see the list-unsubscribe link, the recipient needs to expand the message details by clicking on the small arrow next to where it says “<<Sender>> to me.” This arrow brings down a message details list and the “Unsubscribe from this sender” hyperlink will appear at the bottom.

After the hyperlink is clicked, the following is displayed:

User Interface Features

Gmail Classic

Priority Inbox enabled

While the tabbed inbox is now default, Priority Inbox is still an option for Gmail users.
How to “star” a message  | Primary | Social | Promotins (You may read as well as junk)
A starred promotional message will appear in the Primary Inbox.
Gmail’s Tabbed Inbox and Category Labels
In May of 2013, Gmail further innovated the inbox by releasing a new email productivity feature based on inbox tabs and category labels. Gmail’s tabbed inbox is now the default view for new Gmail accounts, and has been enabled for most existing Gmail users. Although, Gmail users have the option of turning the tabs off.

There are five labels total that are then categorized into their corresponding tab within the inbox. Three of the tabs are on by default (Primary, Social and Promotions), as well as two tabs that can be turned on manually (Forums and Updates). Gmail labels these emails using a special algorithm that looks at everything from content, metadata and user feedback. Most of the categorizations rules came from Smart Labels, a Gmail Labs project that was released in March of 2011 that aimed to automatically label and sort incoming mail.
• Primary - person-to-person conversations and messages that don’t appear in other tabs
• Social – messages from social networks, media-sharing sites, online dating services, and other social websites
• Promotions – deals, offers and most other marketing emails
• Updates – personal, auto-generated updates including confirmations, bills, receipts, and statements
• Forums – messages from online groups, discussion boards and mailing lists

Gmail users have the ability to influence how messages are
labeled by:
  1. Right-clicking and selecting the desired tab from the “Move to tab” menu
  2. Starring a message. The starred message will appear in the primary Inbox, but only that particular message will appear in the primary inbox. Future promotional messages will still be filtered to the Promotions, Social, Updates, or Forums tab.
  3. Dragging and dropping a message into the primary folder. When a user drags and drops a message into a different tab, Gmail prompts users if they would like all future messages from that sender to go to the selected tab. If yes is selected, all messages from that sender will automatically be sent to the primary folder going forward. However, if the Gmail user selects no, messages from that sender will continue to go to the original tab. Below is a campaign from Moosejaw asking their subscribers to move them to the Primary tab.
  4. Selecting the message and choosing a label from the Label Dropdown. If a Gmail user has Priority Inbox enabled, tabs are not displayed. However, the message labels show up in the category views in the side bar. These messages will still appear in the main inbox, and users can click on the category label to view all messages with that particular label.
    Note! If a Gmail user has Priority Inbox enabled, tabs are not displayed. However, the message labels show up in the category views in the side bar. These messages will still appear in the main inbox, and users can click on the category label to view all messages with that particular label.

Article refered from Marketer's Field Guide, ReturnPath 2013

Add new comment autor, 18.04.2019
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