Sendmux alternatives

Quick picks

• Closest match

  

  Mails.aiAutomate cold email outreach with AI-driven marketing
• Free, like Sendmux
  
  Transmitemail infra, byok sending, transactional emails
• Has an API
  
  MailyondOne email inbox for all your domains

1. 1
   

   Mails.ai

   Same job

   Automate cold email outreach with AI-driven marketing

   Claim this listing

   Pick it if you want a closely comparable agent inbox with prompt-injection quarantine flags, scheduled sends and drafts, per-agent reputation scores, and a free tier.

   • Free plan
   • API
   • Web
   • CLI
   Drop-in replacementFreemiumSimilar price to Sendmux

   View Mails.ai
2. 2
   

   Mailyond

   One email inbox for all your domains

   Pick it if you run several products or domains and want to reply as each brand from one inbox, with a hosted MCP server for an assistant to read and answer mail.

   • API
   • Web
   Covers some of itPaidCosts more than SendmuxView Mailyond
3. 3
   

   Transmit

   email infra, byok sending, transactional emails

   Pick it if your main need is marketing campaigns, domain warmup, or sending through your own AWS SES account, rather than giving agents their own mailboxes.

   • Free plan
   • API
   • Web
   Covers some of itFreeCosts more than SendmuxView Transmit

Sendmux and its top 3, side by side

What we compared	SendmuxThis product	Mails.ai #1	Mailyond#2	Transmit#3
What it does	Email inbox API for AI agents	Automate cold email outreach with AI-driven marketing	One email inbox for all your domains	email infra, byok sending, transactional emails
Fit for Sendmux users	—	Drop-in	Covers some	Covers some
Pricing	Freemium	Freemium	Paid	Free
Free plan	Yes	Yes	No	Yes
API	Yes	Yes	Yes	Yes
Open source	No	No	No	No
Platforms	Web, API, CLI	Web, API, CLI	Web, API	Web, API