Gmail has long built a cross-provider inbox entry through "Send as", Gmailify, and POP fetching: users could read external accounts in one Gmail interface, apply Google's anti-spam system, and send emails from their original addresses. This exit signifies Google's retreat from being a "universal inbox aggregator" back to prioritizing its own identities, Workspace, and native Gmail accounts.

From a capital perspective, maintaining third-party email compatibility requires ongoing handling of OAuth authorization, SMTP configuration, POP fetching, anti-spam filtering, troubleshooting, and security responsibilities, but these functions typically do not directly generate advertising or subscription revenue. Google is reallocating resources from marginal compatibility features to its own ecosystem, which can reduce operational and security costs while enhancing the relative attractiveness for individual users to upgrade to Workspace or remain within Google's identity system.

Historically, email clients have concentrated management of different provider emails through POP and IMAP, with Thunderbird, Outlook, and Apple Mail still following this paradigm; Gmailify attempted to unify the traditional protocol layer with Google's anti-spam and categorization capabilities. Its termination does not mean that IMAP or SMTP will become ineffective, but rather that Google is no longer willing to assume the intermediary role of sending and continuous fetching across providers within the Gmail interface.

This represents a restructuring of the industry chain. The competition among email services is no longer just about "who provides free storage", but about who controls identity, inbox entry, anti-spam rules, and migration costs. After Google exits third-party sending, users will need to reselect their email client or service provider, forcing a re-binding of identity and email processing layers; products like Proton's Easy Switch are attempting to capture user data and sending relationships during this migration window.

ABAB News · Cognitive Laws

Once free aggregation stops, users realize that entry points are also infrastructure
Compatibility that doesn't make money for the platform will eventually become users' migration costs
Those who control the sending identity ultimately control user relationships