MarkRelay Research
Email research
Research on email communication as an industry, a technology and a business: who provides it, how it works, what it costs and where it is heading.
- Industry
- Providers and platforms, how the market is shifting, and the rules mailbox providers and regulators set for senders.
- Technology
- Protocols, routing, authentication with SPF, DKIM and DMARC, deliverability, and the infrastructure that carries mail.
- Business
- Pricing, free tiers and limits, business models, and what email really costs at a given volume.
How we work: every fact is traced to a primary source, such as a provider's own documentation, a standard or a public filing, and linked on the page. Each report is dated and keeps a revision log. MarkRelay builds email software, and says so wherever its product is mentioned.
Reports
cloudflare.com
Email Routing and Sending
Updated
site.cloudflare.com Email Routing: free custom domain email, and how to send
Email Routing is free and unlimited on Workers Free and Workers Paid. Each rule sends one address pattern to one verified destination or one Worker.
resend.com
Transactional email
Updated
site.resend.com pricing: free plan, 3,000 emails and 100 a day
Free: 3,000 emails a month, 100 a day, 3 domains, 1 webhook endpoint, 30 days of data, no overage.
brevo.com
Email marketing and SMTP
Updated
site.brevo.com pricing: free plan, 300 emails a day
Free: 300 emails a day after account approval, with REST API, SMTP relay and webhooks.
zoho.com
Custom domain email
Updated
site.zoho.com Mail pricing: free plan for 5 users, and Mail Lite at $1
Forever Free: up to 5 users, 5 GB per user, one custom domain, no IMAP, POP or ActiveSync, available only in select data centers.
fastmail.com
Custom domain email
Updated
site.fastmail.com pricing: custom domain email from $5 a month
Business, per user a month: Basic $3, Standard $5, Professional $9 paid yearly; $4, $6 and $10 paid monthly. Two- and three-year terms cost a little less.
workspace.google.com
Custom domain email
Updated
site.workspace.google.com pricing: Business Starter at $7, and what it costs a team
Per user a month, annual plan: Starter $7, Standard $14, Plus $22. Flexible plan: $8.40, $16.80, $26.40.
Comparison
Custom domain email
Updated
Custom domain email hosting in 2026: Google Workspace, Microsoft 365, Zoho, Fastmail and Proton pricing compared
Cheapest per user: Zoho Mail Lite $1, then Fastmail Basic $3 (no custom domain of its own) and Standard $5, Proton Mail Essentials $6.99, Workspace Starter and Microsoft 365 Basic $7, per month paid yearly.
smtp2go.com
SMTP relay
Updated
site.smtp2go.com pricing: free plan, 1,000 emails a month
Free: up to 1,000 emails a month; sign-up needs an address on a private domain, not Gmail or Yahoo.
mailersend.com
Transactional email
Updated
site.mailersend.com pricing: free plan, 500 emails a month
Free: 500 emails a month, API and SMTP relay, 1 domain, 1 user seat, 100 API requests a day, 1 day of activity data.
Comparison
Transactional email
Updated
Free transactional email API plans compared (2026)
Most free email a month: Resend 3,000 (max 100 a day) and Brevo 300 a day.
mailerlite.com
Email marketing
Updated
site.mailerlite.com pricing: free for 250 subscribers, then Comfort and Power
Free: 250 subscribers, 2,500 emails a month, 2 seats, 3 active automations; the MailerLite logo stays.
mailchimp.com
Email marketing
Updated
site.mailchimp.com pricing: free plan for 250 contacts, and what Essentials and Standard cost
Free: 250 contacts, 500 sends a month, 250 a day; sending pauses over the limit.
substack.com
Newsletters
Updated
site.substack.com fees: 10% of paid subscriptions, and the $50 custom domain
Substack calls itself "free to start and free to leave".
kit.com
Newsletters
Updated
site.kit.com pricing: free for 10,000 subscribers, and what Creator and Pro add
Free Newsletter plan: up to 10,000 subscribers, 1 user, unlimited broadcasts, forms and landing pages, selling digital products and subscriptions; no visual automation builder.
beehiiv.com
Newsletters
Updated
site.beehiiv.com pricing: free for 2,500 subscribers, then Lite and Pro
Free: up to 2,500 subscribers; no paid subscriptions and no ad network.
ghost.org
Newsletters
Updated
site.ghost.org pricing: Ghost(Pro) from $18 a month, and 0% on paid newsletters
Per month billed yearly, at 1,000 members: Starter $18 (1 staff user), Publisher $29 (3), Business $199 (15).
Comparison
Newsletters
Updated
Newsletter platforms in 2026: Substack, beehiiv, Kit, Ghost, MailerLite and Mailchimp pricing and fees compared
Largest free plans: Kit 10,000 subscribers, beehiiv 2,500, MailerLite 250, Mailchimp 250; Substack is free to publish without a limit.
Standards
Deliverability
Updated
Gmail, Yahoo and Outlook bulk sender requirements: SPF, DKIM, DMARC and one-click unsubscribe
Every sender to Gmail and Yahoo: SPF or DKIM, valid forward and reverse DNS for sending IPs, spam rate below 0.3%, messages formatted to RFC 5322.
support.google.com
Gmail changes
Updated
site.support.google.com: Gmail ends POP fetching, Gmailify and Send as for other addresses
Ending in January 2027: Gmail fetching mail from third-party accounts over POP, Gmailify, and "Send as" for third-party addresses.
support.google.com
Gmail setup
Updated
site.support.google.com: Gmail Send mail as with your own domain, and why it stops working in 2027
Send as adds an address to Gmail's From menu after a confirmation email to that address.
support.google.com
Team email
Updated
site.support.google.com: Workspace shared inbox, delegation and collaborative inbox compared
Shared inbox: delegates can read, send and delete; supported on Business Starter, Standard and Plus; released in phases.
developers.cloudflare.com
Email Routing and Sending
Updated
site.developers.cloudflare.com: what Email Workers can do, and where they stop
email(message, env, ctx) receives from, to, headers, raw, rawSize and canBeForwarded.
cloudflare.com
Email Routing and Sending
Updated
site.cloudflare.com: the DNS records for Email Routing and Email Sending
MX: route1.mx.cloudflare.net, route2.mx.cloudflare.net, route3.mx.cloudflare.net, with priorities assigned by Cloudflare.
Comparison
Team email
Updated
Catch-all email compared: Cloudflare, Google Workspace, Fastmail, Migadu and MarkRelay
Cloudflare: one catch-all rule per domain with three actions, send to an email, send to a Worker, or drop; plus addressing matches the base rule.
Comparison
Inbound email
Updated
Inbound email to webhook compared: Resend, Mailgun, SendGrid, Postmark, Cloudflare and MarkRelay
Resend: event email.received; the webhook has metadata only (IDs, from, to, subject, attachment list); body and attachments come from its API.
microsoft.com
Custom domain email
Updated
site.microsoft.com: Microsoft 365 Business Basic at $7, and email-only Exchange at $4
Business Basic: $7 per user a month paid yearly, $8.40 monthly; up to 300 users; web and mobile Office apps and custom business email.
proton.me
Private email
Updated
site.proton.me business mail pricing: from $6.99 a user, with custom domains and catch-all
Mail Essentials: $6.99 per user a month billed yearly ($83.88 a year), 15 GB, 3 custom domains, 10 addresses per user.
aws.amazon.com
Transactional email
Updated
site.aws.amazon.com SES pricing: $0.10 per 1,000 emails, and what comes with it
Outbound: $0.10 per 1,000 emails, plus $0.12 per GB of attachments.
postmarkapp.com
Transactional email
Updated
site.postmarkapp.com pricing: from $15 for 10,000 emails, inbound from Pro
Free: 100 emails a month, no overage, up to 10 sending domains.
mailgun.com
Transactional email
Updated
site.mailgun.com pricing: free plan, 100 emails a day, and inbound routes by plan
Free: 100 emails a day, 1 custom domain, 1 inbound route, 1-day logs, 1 user.
sendgrid.com
Transactional email
Updated
site.sendgrid.com: the free plan is retired. What changed, and where to send for free now
Free Email API and Free Marketing Campaigns retired starting May 27, 2025, with 60 days of continued access for existing free users.
Comparison
AI agents
Updated
Email MCP servers compared: Resend, Postmark, MailerSend, AgentMail, SendGrid and MarkRelay
Hosted remote servers with OAuth: Resend (mcp.resend.com/mcp, or an API key), MailerSend (mcp.mailersend.com/mcp), AgentMail (mcp.agentmail.to/mcp, or an x-api-key header).
Sites
Reports filed by the site they study. A report about one site is titled after it, as in site.cloudflare.com.
cloudflare.com
2 reports
resend.com
1 report
brevo.com
1 report
zoho.com
1 report
fastmail.com
1 report
workspace.google.com
1 report
smtp2go.com
1 report
mailersend.com
1 report
mailerlite.com
1 report
mailchimp.com
1 report
substack.com
1 report
kit.com
1 report
beehiiv.com
1 report
ghost.org
1 report
support.google.com
3 reports
developers.cloudflare.com
1 report
microsoft.com
1 report
proton.me
1 report
aws.amazon.com
1 report
postmarkapp.com
1 report
mailgun.com
1 report
sendgrid.com
1 report
MarkRelay sells a self-hosted email app that runs on Cloudflare and is not affiliated with the vendors covered here. Found something outdated? Tell us and we will re-check it.