Here's what happened.
" \ --yes # Attachments (repeat --attach for multiple files) nylas email send --to team@company.com \ --subject "March report" \ --body "Attached is the report." \ --attach ./march-report.pdf --attach ./appendix.xlsx \ --yes # CC and BCC nylas email send --to alice@team.com \ --cc bob@team.com --bcc manager@team.com \ --subject "Project status" \ --body "All tasks on track for Friday." \ --yes ``` iCloud Mail caps attachments at 20 MB per message. Apple's Mail Drop (which absorbs files up to 5 GB) runs only in Apple Mail and at iCloud.com. It isn't exposed through SMTP or any public API, so it isn't available from the terminal either. ## 4. Send from a custom domain or Hide My Email alias This is the iCloud-specific feature that matters most. An iCloud+ subscription (starting at $0.99/month for the 50 GB tier) unlocks up to 5 custom email domains and unlimited Hide My Email relay addresses. Once a domain is verified in iCloud settings, you can send from any address on it with `--from`: ```bash # Send from your custom domain nylas email send \ --to client@example.com \ --from hello@yourdomain.com \ --subject "Invoice #1042" \ --body "Please find your invoice attached." \ --attach ./invoice-1042.pdf \ --yes # Send from a Hide My Email relay nylas email send \ --to newsletter@service.com \ --from abc123@privaterelay.appleid.com \ --subject "Unsubscribe" \ --body "Please remove me from your list." \ --yes ``` Hide My Email relays forward incoming mail to your real inbox; recipients only see the relay address. The same mechanism powers Sign in with Apple's private relay. ### Custom domain DNS setup Before a domain can send, Apple requires three DNS records at your registrar. From [Apple's iCloud custom domain docs](https://support.apple.com/guide/icloud/set-up-a-custom-email-domain-mm9ac9480988/icloud): | Record | Purpose | Value Apple provides | | --- | --- | --- | | MX | Route inbound mail to iCloud | `mx01.mail.icloud.com` and `mx02.mail.icloud.com` (priority 10) | | TXT (SPF) | Authorize Apple to send on your behalf | `v=spf1 include:icloud.com ~all` | | TXT (DKIM) | Sign outbound messages | Unique per domain; Apple generates when you add the domain | Propagation usually finishes inside an hour but Apple can take up to 72 hours to verify. The CLI surfaces a clean "sender domain not verified" error until verification completes, so it's safe to queue sends before DNS finishes propagating. ## 5. JSON output for scripting Add `--json` to any command for structured output. Useful when piping into `jq`, logging, or feeding another process. ```bash nylas email send --to user@example.com \ --subject "Automated alert" \ --body "Build failed: see logs." \ --yes --json | jq '.id' ``` --- ## iCloud SMTP vs the CLI | Step | iCloud SMTP | Nylas CLI | | --- | --- | --- | | Enable 2FA on Apple ID | Required | Handled by the Nylas OAuth flow | | Generate app-specific password | Required per script | Not used | | SMTP host/port | smtp.mail.me.com:587 (STARTTLS) | Not exposed | | Token refresh | No (static password) | Automatic | | Custom domain sending | Per-domain SMTP config | `--from` flag | | Hide My Email send | Not possible via SMTP | `--from` flag | | Scheduled delivery | Not supported | `--schedule` flag | | JSON output | Not supported | `--json` flag | ## Apple-specific sending details ### Daily sending limits Apple's [iCloud system requirements](https://support.apple.com/en-us/102149) page caps iCloud Mail at 1,000 outbound messages per day and 500 recipients per message (To + CC + BCC combined). The 24-hour window is rolling, not a calendar-day reset. Apple doesn't publish the short-burst throttle, so sustained bursts can trigger temporary delays before you hit the daily cap. ### Hide My Email limits Paid iCloud+ plans get unlimited Hide My Email addresses. Generate them from Settings > Apple ID > iCloud > Hide My Email on iOS, or from [icloud.com/settings](https://www.icloud.com/settings/) on the web. Once a relay is deactivated, new mail to that address stops forwarding. ### Custom domain caps iCloud+ permits 5 custom domains per account. Custom domains are included with iCloud+ features that can be shared through Family Sharing. If DNS records change after verification, Apple suspends outbound sending on that domain until the records match again. ### Why Mail Drop doesn't work from the terminal Apple's Mail Drop uploads attachments over 20 MB to iCloud servers and sends a download link instead of the file. The feature is bolted onto Apple Mail and the iCloud.com web client; it isn't exposed through SMTP or any public API. For large files from the terminal, upload to a shareable location and send the link in the body. ## Troubleshooting iCloud sends ### "Sender domain not verified" on custom-domain sends Apple won't let a custom domain send until its MX, SPF, and DKIM records are all visible at the authoritative nameservers. Check propagation with `dig MX yourdomain.com +short` and `dig TXT yourdomain.com +short`. If the records look right but Apple still rejects, wait. Apple re-checks DNS periodically, and verification can take up to 72 hours. ### "550 5.7.1 Message rejected due to local policy" iCloud's outbound filter flagged the message. Common causes: the body contains URL shorteners (`bit.ly`, `tinyurl`), the subject is a single word, or the message went to a large BCC list with identical body text. Rewrite the body with the real destination URL and break up large BCC runs. ### Sending suddenly stops after a batch run You've tripped the 1,000-message daily cap. The block lasts 24 hours from the 1,001st message, not from midnight Pacific. For higher throughput, connect a second iCloud+ account or move bulk email to a dedicated transactional provider. iCloud Mail isn't designed for campaign traffic. ### OAuth consent loop during the initial mailbox connection If Apple's consent screen shows "Something went wrong" while connecting the mailbox in the Nylas dashboard, the Apple ID likely has a pending 2FA trust prompt on another device. Open Settings > Apple ID on any signed-in device, accept any pending prompts, then retry the mailbox connection. ### Replies to a Hide My Email send bounce back If replies are bouncing, check Settings > Apple ID > iCloud > Hide My Email and confirm the address isn't set to "Deactivate". The UI shows deactivated addresses greyed out but still lists them, so it's easy to miss that a relay was turned off earlier. ## Next steps - [Send email from the command line](https://cli.nylas.com/guides/send-email-from-terminal) -- the general guide covering all providers - [List iCloud emails from terminal](https://cli.nylas.com/guides/list-icloud-emails) -- read and search your iCloud inbox - [Manage iCloud calendar from the CLI](https://cli.nylas.com/guides/manage-icloud-calendar-cli) -- events, reminders, and scheduling - [Give AI agents email access via MCP](https://cli.nylas.com/guides/ai-agent-email-mcp) -- connect Claude, Cursor, or VS Code to your mailbox - [Full command reference](https://cli.nylas.com/docs/commands) -- every flag and subcommand documented