InboxWarm.ai vs WarmEnvelopes

InboxWarm.ai automatically warms Gmail, Outlook, and SMTP inboxes to build sender reputation, improve inbox placement, and reduce spam placement. It sends, opens, and replies to warmup messages using contextual replies generated by large language models and human-like sending patterns. InboxWarm describes its seed network as private and made up of real inboxes. Its spam recovery feature marks warmup messages as not spam and moves them to the primary inbox when they land in spam. Supported setups include Gmail, Outlook, SendGrid, Amazon SES, Mailgun, Yahoo, and custom SMTP/IMAP. Plans include SPF, DKIM, and DMARC domain-health monitoring and real-time inbox-placement tracking. Every plan includes a public REST API with 30 endpoints; the default rate limit is 20 requests per minute per API key. Monthly prices range from $15 a month for one mailbox to $5 a month for 51–100 mailboxes, with up to 100 warmup emails per inbox per day on those listed tiers. A 10-day trial covers one email account without a credit card.

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.