Best Gmail Extensions for Tracking Deadlines (2026)

Boomerang is the most established player in email productivity, with over 10 years in the market. Its core strength is email scheduling and follow-up tracking. You can schedule emails to send later, set reminders if you don't get a reply, and "boomerang" emails back to your inbox at a specific time.

For deadline tracking, Boomerang requires manual work - you need to actively boomerang each deadline email. It does not automatically detect deadlines. However, if your workflow is primarily about following up on sent emails and scheduling sends, Boomerang excels. The "Respondable" AI feature that scores email effectiveness is genuinely useful for sales teams.

Sortd transforms Gmail into a Trello-like board view. You create lists (like "To Do", "In Progress", "Done") and drag emails between them. It is a fundamentally different approach - instead of processing emails in a linear list, you organize them spatially.

For deadline tracking, Sortd offers due dates on tasks and email reminders. But like Boomerang, you need to manually add deadlines - there is no auto-detection. The strength is visual workflow management, especially for people who think in boards rather than lists. Teams get shared boards for collaborative email triage.

Todoist is not primarily an email tool - it is a full-featured task manager with excellent Gmail integration. The Gmail plugin lets you turn emails into Todoist tasks with one click, complete with due dates, projects, and priorities.

If you already use Todoist for task management, this is a natural choice. Emails become tasks in your existing workflow. The free tier is generous (5 projects, basic features). However, there is no deadline auto-detection - you manually create tasks from each email. The strength is the broader task management ecosystem, not email-specific features.

FollowUpThen is beautifully simple: forward or BCC an email to an address like "3days@followupthen.com" and it returns to your inbox in 3 days. No extension needed, works with any email client. You can also use it for recurring reminders (every month, every Friday, etc.).

The elegance is that it works everywhere - Gmail, Outlook, mobile, any device. No installation required. The downside is that it is entirely manual and there is no interface for seeing all your scheduled reminders without checking your FollowUpThen account. For power users, Boomerang offers more features. For simplicity purists, FollowUpThen is unbeatable.

SaneBox focuses on email triage - automatically sorting incoming mail into folders like SaneLater (not urgent), SaneNews (newsletters), and SaneBlackHole (never see again). The "SaneRemindMe" feature lets you snooze emails to return later.

The unique angle is AI-powered prioritization that learns from your behavior. SaneBox trains on which emails you read, reply to, and ignore. Over time, it gets better at surfacing important emails. For deadline tracking specifically, it is limited - you can snooze emails, but there is no deadline detection. The value is reducing inbox noise so deadline emails are more visible.

Mailbutler is unique in supporting Apple Mail alongside Gmail and Outlook. If you are a Mac user who prefers the native Mail app, Mailbutler is one of your few productivity options. Features include send later, tracking, snooze, templates, and task creation.

The task feature creates tasks from emails with due dates, similar to Todoist. Email tracking tells you when recipients open emails. For deadline tracking, it is manual - you create tasks from deadline emails. The strength is cross-platform support and solid execution on core productivity features.

Mixmax is built for sales and revenue teams. Its killer features are email sequences (automated follow-up campaigns), one-click meeting scheduling embedded in emails, and detailed engagement analytics. You can see exactly when prospects open emails, click links, and view attachments.

For general deadline tracking, Mixmax is overkill. But if your deadlines involve sales pipelines, contract renewals, or client follow-ups, the sequence and tracking features are powerful. The free tier is surprisingly capable for individual use. The jump to paid is steep ($29/month) but includes features that compete with dedicated sales engagement platforms.

Right Inbox is a direct Boomerang competitor with similar features at a lower price point: email scheduling, reminders, tracking, and recurring emails. The interface is clean and lightweight - it does not slow down Gmail like some heavier extensions.

The free tier offers 10 actions per month (vs Boomerang's 10 credits). Paid plans are more affordable than Boomerang. If you need Boomerang-style features but want to save money, Right Inbox is worth considering. For deadline tracking specifically, it requires manual work like all the scheduling-focused tools.

Gmail's built-in snooze feature is the simplest option: click the clock icon, choose when to be reminded, and the email disappears then reappears at that time. No extension needed, works on web and mobile, completely free.

The limitations are significant for deadline management. You can only snooze once (no recurring reminders). There is no overview of snoozed emails beyond the "Snoozed" label. And you must manually snooze each deadline email. However, if you only deal with a handful of deadlines and want zero additional tools, Gmail snooze works.