Resend is one of the cleanest developer experiences in email, which makes it tempting for cold email. It is the wrong tool for the job, for the same reasons Postmark is: design, policy, and reputation.
Resend is built for transactional mail: account events, receipts, alerts, the mail a user expects because they did something. The API, the defaults, and the documentation all assume that relationship. Cold email has no prior relationship, and the platform has no machinery for it: no warmup tooling, no outreach features, no complaint management tuned for cold lists.
Resend's acceptable use policy restricts unsolicited bulk email. Running a cold outreach campaign on Resend is a terms violation, and a younger provider has less to lose by enforcing it. The account risk is real: suspension stops your sending cold, including the transactional mail you do want to send.
Resend sends from shared infrastructure by default, and that infrastructure is newer than SendGrid's or Mailgun's. Newer shared IPs have less history with mailbox providers, and cold email is the fastest way to write a bad history. You would be spending the reputation of a young provider on the use case that burns reputation fastest.
Keep Resend for the transactional mail it is good at. For cold email, use a separate sending domain, a provider that explicitly permits outreach (a dedicated cold-email tool or a transactional provider with a dedicated IP and the right terms), proper SPF, DKIM and DMARC on that domain, and a two to four week warmup starting at 10 to 20 emails a day. The two systems never share a domain, so the cold-email risk never touches your transactional mail.
Whichever provider you pick, the setup on your domain decides the outcome.
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