Skip to main content
Send emails to your users directly from inside your Hercules app. Send emails from a free Hercules email or from your own branded email address.

​
How do I get started?

  1. Go to the Emails tab
  2. Verify a single email or an entire domain
  3. That’s it!
Now just tell Hercules when you want to send an email
Email sending examples

​
What are common use cases for sending emails from within my app?

  • Welcome emails when a new user signs up
  • Form submissions
  • Invoices for a purchase
  • Order confirmations after a purchase
  • Account alerts like login from a new device

​
How do I send emails to all my users?

Go to the horizontal Send email tab

​
Suppression list

Some addresses should never be emailed again: a mailbox that no longer exists, or a recipient who reported your email as spam. Hercules keeps a suppression list of those addresses and refuses to send to them, which is what protects your ability to reach everyone else. An address gets on the list three ways:
  • Bounced — the recipient’s mail server permanently rejected the message.
  • Marked as spam — the recipient reported your email as spam.
  • Added by you — you put it there from the dashboard or the API.
The first two happen automatically. The list belongs to your organization and covers every app and sender address you own, so an address suppressed in one app is suppressed in all of them. It is yours alone — no other Hercules customer’s bounces affect it. To manage it, go to the Emails tab and open Suppressions. From there you can add an address, import a CSV (or a plain list, one address per line), export the whole list, and allow an address again.
Removing an address does not guarantee delivery. If it bounces or is reported as spam again, it goes straight back on the list.

​
FAQ

  1. Go to the Emails tab
  2. Input the email address you want to send from.
  3. Click the verification link we send to that email
Once verified, Hercules will be able to send emails from that email address
  1. Go to the Emails tab
  2. Input the domain you want to send from.
  3. Follow the instructions to add the DNS records to your domain’s nameservers
Once your email sending domain is verified, Hercules will be able to send emails from any email address with that domain.
  1. Go to the Emails tab
  2. Input the Hercules domain you purchased.
  3. Follow the instructions to add the DNS records to your domain purchased on Hercules.
  4. Go to your Hercules purchased domain in the Domain page.
  5. Click DNS Records under you domain.
  6. Click + Add Record and add your DNS records.
Once verified, Hercules will be able to send emails from any email address with that domain.
Yes. Ask Hercules to update the design of your emails. You can change colors, layout, logo, and content by describing what you want.
Failed emails show up as bounced in the Emails tab with a reason. Hercules stops sending to addresses that permanently bounce to protect your sender reputation, by adding them to your suppression list. You can remove an address from that list yourself.
Yes. Open the Emails tab, click the sliders icon above the history table, and switch on Cc, Bcc, Reply-to, or Email ID — the id is the handle the email API reads a single message by, and the one thing the detail panel does not show. Your choice is remembered in this browser, and Reset to default in the same menu puts it back.
The recipient is on your suppression list, so the send was rejected before it left Hercules. That is deliberate — it costs you nothing and cannot hurt your sender reputation.Go to the Emails tab, open Suppressions, find the address, and choose Allow email again if you are confident the mailbox is now working. Bear in mind that whatever put it on the list will put it back if it happens again.
Yes. Go to the Emails tab, open Suppressions, and choose Add address — or import a whole list from a CSV. Hercules will refuse to send to it from any of your apps until you remove it.
Verifying an email address lets you send from that specific email address. Verifying a domain lets you send from any email address on that domain. Email verification is faster (click a link), while domain verification requires adding CNAME records to your DNS.
Yes. Your plan sets a monthly limit, and a daily cap sits underneath it.Your monthly limit, counted across the trailing 30 days:
  1. Free: 100 emails / month
  2. Pro: 10,000 emails / month
  3. Business: 100,000 emails / month
Your daily cap is a tenth of that, counted across the trailing 24 hours:
  1. Free: 10 recipients / day
  2. Pro: 1,000 recipients / day
  3. Business: 10,000 recipients / day
The daily cap counts recipients, not sends. Every address in To, Cc, and Bcc counts as one, so a single send to 30 people uses 30 of the day’s allowance. Only emails you send through the API draw from it. Sign-in emails do not.Sending at an even pace uses about a thirtieth of your monthly limit each day, so the cap leaves roughly three times that for a busy day, while stopping a runaway loop from spending a whole month’s allowance at once.Broadcasts are the usual way to meet it. Sending to more recipients than the day’s remaining allowance delivers the first few and rejects the rest with a 429, so a list larger than your daily cap needs to be split across days. Capacity returns gradually rather than all at once, as earlier sends age out of the trailing 24-hour window.On the legacy Lite plan, both limits match Pro.If you need to send more emails, please contact support.
Separately from your monthly and daily limits, your organization can send at most 10 emails per hour to any one address in the To field. This guards against a single inbox being flooded. Only your own sends count towards it, so nobody else’s sending can use up your allowance, and it is the same on every plan, so upgrading does not raise it.Sign-in emails share the allowance only if you have set your app to send them from your own verified address. When you have, sending 10 test emails to your own address also blocks your own login codes for the rest of the hour. If your app still uses the default Hercules sign-in email, those codes go out through a separate sender and are not affected.It most often shows up while testing, when every test email goes to the same address. Every other address has its own allowance, so vary the recipient between test runs (many mail providers let you add a suffix, such as you+test1@example.com) or wait until the hour has passed.
You can add up to 50 custom tags to an email. Each tag name and value must be 1-256 characters. The name can use only ASCII letters (A-Z and a-z), numbers (0-9), underscores (_), or dashes (-). The value can also use periods (.) and at signs (@). Spaces and other punctuation are rejected before the email is sent. The 400 response identifies the invalid field, for example tags.0.value.
Email tags
No. Hercules Emails handles everything. No external provider or API key is required.
This means no sender has been set up for your organization yet. It shows when hercules.email.send() runs before you verify a sender.
  1. Go to the Emails tab
  2. Verify an email address or a domain
  3. Send from that verified address
Once a sender is verified, the error clears.
Your domain or email may be verified however, you may still be seeing an error when trying to send an email saying “Sender ‘hello@my-domain.com’ is not a verified identity for this website” when calling hercules.email.send().This usually automatically resolves itself within 5 minutes. This is a known issue we are actively investigating. If it persists after 5 minutes, please report an issue.
For platform auth and OTP emails, allowlist hercules.app and notifications.hercules.app. For emails sent via the Email SDK (hercules.email.send()), the sending domain is your own verified domain (configured in your app’s Emails tab). If your corporate mail system flags emails as a new sender, have IT allowlist the relevant domain.
Inbound email (receiving) is not yet available. It is currently under construction, with no confirmed timeline. Hercules will notify users when it launches.In the meantime, you can receive emails at your domain by setting up a third-party email provider (Gmail, Outlook, and similar) via MX records: Domains → Manage DNS → + Add record → MX.
  1. Check your Hercules email configuration setup. Make sure your email is properly set up and says “verified”.
  2. Make sure your email domain is correctly configured Use the following 3rd party tools to confirm everything is configured correctly:
  1. Check public spam reports. Use the following 3rd party tools to see if your domain is flagged:
  1. Test deliverability. Send a test email to a public inbox and check where it lands:
Finally, you can also investigate 3rd party “mail warming” tools