InboxPlan vs WarmEnvelopes

InboxPlan is a web service for automated email warm-up, scheduling, and deliverability monitoring. It creates warm-up messages and simulated two-way conversations tailored to a user's industry, then schedules activity with randomized send windows and a gradual increase in volume. InboxPlan says sending typically starts at 3–5 emails per day in week one and reaches 30–50 per day by week four; users can set manual limits for each account. A live monitor tracks sender score, inbox placement, and spam rates across major providers. Users can connect Gmail, Outlook, Zoho, or custom SMTP accounts and warm multiple mailboxes in one workspace, subject to the plan's account allowance. Each account receives its own threads, schedule, and reputation dashboard. InboxPlan says it uses OAuth and does not store account passwords. It names sales teams, agencies, and startups among its intended users, as well as businesses in SaaS, recruiting, real estate, finance, and e-commerce. The service is paid, with no free plan, and offers a 7-day free trial that requires a credit card. InboxPlan was founded in 2022 and is headquartered in San Francisco, California.

WarmEnvelopes is a web service that schedules genuine warm-up emails from a configured domain through the user’s Resend account. Messages go to inboxes the user controls, or whose owners have consented, to build sending history. Setup requires a verified sending domain and a Resend API key, with a separate key stored for each domain. A scheduler runs every 30 minutes and spreads the daily target across the day. Pro users can set starting volume, daily increases, and a maximum. The library contains more than 1,000 independently written messages in several languages, varying templates and sender names. Each send records its sender, template, delivery status, and errors, while the dashboard shows daily progress. The Free plan costs 0.00 EUR and permits four emails per day per domain across up to 10 domains. Pro costs €9 a month and supports up to 1,000 daily emails. A separate checker reviews SPF, DKIM, DMARC, MX, and blocklist status.