Transmit

Most email providers have a dirty secret: they pool thousands of customers onto shared IP addresses. When one sender on that IP gets flagged for spam, the reputation hit affects everyone. Your carefully crafted transactional emails start landing in spam folders, not because of anything you did, but because a stranger on your shared IP was sending junk. SendGrid's shared IPs were blocked by Microsoft for 36 hours. About 17.5% of emails on shared infrastructure route to spam globally.

Transmit was built to fix this. Every customer gets their own isolated sending infrastructure. Not a logical separation in software. Real isolation at the cloud level. Your sending reputation is yours alone, and nobody else's behavior can affect your deliverability. The result: 99.2% inbox placement across all customers.

Transmit runs in two modes, and you can switch between them without changing a single line of code.

**Managed mode** is the fastest way to start sending. Sign up, add your domain, and you're live in under two minutes. Transmit handles all the infrastructure: dedicated sending environment, automated domain warmup (1.5x/day exponential ramp-up with auto-pause on high bounces), one-click DKIM, SPF, and DMARC setup, and built-in email validation to block invalid and disposable addresses before they hurt your reputation. Plans start at $2/mo for 3,000 emails.

**BYOK mode** (Bring Your Own Keys) is for teams that want full control. Connect your own AWS SES account and keep $0.10 per 1,000 email pricing. Transmit adds everything SES is missing: a campaign builder, contact management, real-time analytics, automated warmup, inbound email routing, and searchable message logs. You can connect via IAM Role assumption (recommended, uses temporary STS tokens with no stored secrets) or access keys (AES-256-GCM encrypted at rest, decrypted only in-memory during sends). At 1M emails per month, BYOK mode costs $249 total, compared to $650+ on other platforms.