Mailroom / vs GMass
Mailroom vs GMass:
the free, open-source alternative.
GMass is the market-leading paid bulk-email Chrome extension for Gmail. It works well, has been around since 2015, and offers advanced features like email warm-up, A/B testing, and behavior-triggered follow-ups. It also costs $25–$125 per user per month and locks scheduling, open tracking, and most automation behind paid tiers. Mailroom is the free, open-source alternative for the 90% of senders who just need CSV mail merge and personalized sends.
TL;DR
Pick Mailroom if
- Free forever, no trial expiry, no credit card
- Open source (MIT) — you can audit and self-host every line
- Scheduling and bounce detection in the free tier
- No Chrome extension required — works in any browser
- Your data lives in your own Supabase, not on a vendor's server
Pick GMass if
- Email warm-up service to build Gmail sender reputation from scratch
- Built-in A/B testing on subject lines and body copy
- Behavior-triggered follow-up sequences
- 10+ years of enterprise polish and integrations
Feature-by-feature comparison
GMass is the most popular paid Gmail mail-merge extension, priced at $25–$125/mo per user, with a free tier of limited trial (50 sends/day for 30 days). GMass runs as Chrome extension that sits inside the Gmail web UI.
| Mailroom | GMass | |
|---|---|---|
| Pricing | $0 | $25–$125/mo |
| Free tier | 500/day forever | 30-day trial, 50/day |
| Schedule sends | Yes (free) | Paid only |
| Open tracking | Yes (free) | Yes |
| Click tracking | Coming soon | Yes |
| Bounce detection | Auto (free) | Auto |
| Mail merge tags | Yes | Yes |
| Sends from your Gmail | Yes (via API) | Yes (via extension) |
| Chrome extension required | No | Yes |
| Open source | Yes (MIT) | No |
| Self-host | Yes | No |
| Daily limits respected | Yes (500/2000) | Yes |
| A/B testing | No | Yes (paid) |
| Email warm-up | No | Yes (paid) |
| Auto follow-ups | No | Yes (paid) |
FAQ: switching from GMass
Is Mailroom a true GMass alternative?
For the core use case — sending a personalized bulk email to a CSV list from your Gmail — yes. Mailroom does mail merge, scheduling, open tracking, bounce detection, and unsubscribe handling for free. GMass adds warm-up, A/B testing, and automated follow-ups, which Mailroom does not (yet) replicate. If you only need the basics, Mailroom saves you $25–$125/month.
Will Mailroom hurt my Gmail deliverability the way GMass might?
No — both tools send through your own Gmail account, so your sender reputation is your own in either case. Deliverability depends on list hygiene (no spam traps), warm-up history, and content (no spammy phrases), not on which tool dispatches the API call. Mailroom enforces an unsubscribe footer and suppression list specifically to keep your reputation clean.
Can I migrate from GMass to Mailroom?
Yes — just export your contacts as CSV, sign into Mailroom with the same Gmail account, and upload. Mailroom doesn't import GMass-specific data like A/B test results, but your recipient list and merge fields transfer directly.
Why is Mailroom free when GMass charges $25+/month?
Mailroom is a side project — it runs on Vercel's free tier and a Supabase free tier, and the developer pays the few dollars of overage out of pocket. GMass is a venture-funded business with a 30-person team. The trade-off is honest: GMass has more features and more polish; Mailroom has the core 80% for $0.
Save the $25 and just send the email.
Connect Gmail, upload your CSV, hit send. Free forever.
Start with Mailroom