Gmail is Google’s free email service. Released to the general public in February 2007, the advertising-supported service is similar to offerings from Yahoo, AOL, and Microsoft.
Users commonly access Gmail as secure webmail, although clients exist for popular mobile platforms like iOS and Android. Users can also access their mail via both the POP3 and IMAP4 protocols for use in the email client of their choice.
Gmail currently ranks #8 in our email client market share reporting, with 3% of opens being attributed to the service. While still a popular webmail client, it currently ranks behind both Outlook.com (#6) and Yahoo Mail (#7).
It’s interesting to note that Gmail has seen a steady decrease in market share over the past few months, likely do to the increasing popularity of mobile email clients, which have seen huge gains over the past year.
Gmail largely relies on a community-driven spam filter for analyzing messages, not unlike most email providers. Gmail differs in that it does not disclose the use of blacklists, whitelists, or feedback loops for senders.
While this can be problematic for senders used to working with ISPs and email providers on deliverability issues, Google does have some helpful guidelines for bulk senders.
In 2013, Google introduced Gmail’s “new inbox”. Emails are automatically sorted into one of the following five tabs: Primary, Social, Promotions, Updates, and Forums. Users have the ability to customize tabs and define rules for sorting emails from particular senders. Similar to the way it filters spam, Google takes into account how users categorize emails and uses that information when determining how to filter future emails.
Many marketers voiced concerns about the “new inbox” affecting deliverability and opens for their campaigns. While there have been reports of open-rate drops, the “new inbox” is still a bit too new for definitive guidelines on how campaigns are affected or workarounds for the new tabs.
The Gmail webmail client relies on the browser it is running in for rendering HTML emails. This means that similarly styled content can vary in appearance whether viewed in Internet Explorer, Chrome, Safari, Firefox, etc. The operating system can also affect the display of content, as Windows, OS X, and Linux all display things like text slightly differently.
Gmail also blocks images by default, displaying an alert above the email prompting users to enable images for the email.
You will want to take this into account and always include appropriate alt-text for your images to insure that your message gets across to subscribers even when images are disabled.
While most common selectors work in Gmail, it has extremely limited support for pseudo-selectors such as :hover and :first-child. Most designers don’t take advantage of pseudo-selectors in email, but for those attempting some hover effects, keep in mind that they will not work in Gmail.
Gmail does support most of the box-model, allowing designers to use padding, margins, width, height, and min- and max- for structuring content. However, Gmail does not support most positioning rules for CSS - including top, right, bottom, and left. Oddly enough, it does support the use of floats and clears. Designers that are using display:none; to hide content on devices will find Gmail frustrating, as it does not support the property at all.
Those looking to use CSS3 to embellish their designs will find that Gmail does not render commonly used properties like text-shadow and box-shadow. Border-radius works well, though.
Email Client Market Share
Campaign Monitor's Will It Work?
MailChimp's CSS Support Guide
Campaign Monitor's Guide to CSS Support
How Gmail's Spam Filter Works
How Gmail's New Inbox is Affecting Open Rates
Why Preprocessors are the Enemy
Why Do Email Clients Render Emails Differently?
Why Email Designs Break