Activity

Helo gives you full visibility into every email you send. From the moment a message is accepted to the moment it’s delivered, opened, or bounced, every event is captured and queryable — in real time. Activity comes in two forms:

• Events — an ordered log of every delivery lifecycle event for every message
• Messages — a view of each distinct message along with its full delivery history

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Events

Every message goes through a series of lifecycle events as it moves through Helo’s infrastructure.

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Querying events

You can retrieve events via the API with a wide range of filters: Results are paginated using a cursor. Pass the after value from a response to fetch the next page. Each page returns up to 500 events.

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Messages

The messages view gives you a higher-level perspective — one record per distinct message sent, each with a summary of its delivery status and recipient list. Each message has:

• A unique messageId
• The channelId it was sent through
• mailType (transactional or broadcast)
• mailSource (api or smtp)
• deliveryType (live or sandbox)
• status (queued or sent)
• Subject, recipients, and tags

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Message details

Fetching a single message by ID returns the full picture:

• Headers — from, to, cc, bcc, reply-to addresses
• Content — plain text body, HTML body
• Attachments — filename, disposition (inline or attachment), and size
• Tracking settings — whether open tracking and link tracking were enabled
• Events — the complete ordered history of events for that message

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Querying messages

Messages support the same filters as events: channelId, startDate/endDate, recipient, subject, tags, mailType, and status. Results are paginated up to 100 per page.

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Statistics

Helo aggregates your sending data into statistics so you can understand trends and monitor the health of your sending over time. Stats are always broken down by mail type — transactional and broadcast — so you can see how each sending stream is performing independently. The following metrics are tracked:

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Time-based aggregations

Stats are available at three granularities:

• Hourly — one data point per hour, for a given from/to range
• Daily — one data point per day, for a given from/to range (pass a timezone to align days to your local time)
• Totals — a single aggregated summary for the entire from/to range

All three endpoints support filtering by channelId and by tags.

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Channel deliverability

Helo monitors the deliverability health of each channel and will alert you when metrics approach problematic thresholds. Each channel receives a health score: Health is calculated as (sent - bounced) / sent, separately assessed across both mail types and then combined.

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Deliverability alerts

When bounce rates or spam complaint rates exceed safe thresholds, Helo generates an alert. Alerts have two severity levels: Bounce rate alerts: Spam rate alerts: These thresholds reflect industry standards set by major inbox providers (Gmail, Yahoo) for acceptable sending behavior. Consistently exceeding them risks inbox placement, domain/IP reputation damage, and may trigger account suspension.

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Bounces

A bounce means an email could not be delivered. Helo tracks two types of bounces, which behave differently and require different responses.

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Hard bounces

A hard bounce is a permanent delivery failure. The receiving server has definitively rejected the message. Common causes include:

• The recipient email address does not exist
• The domain does not exist or has no mail server
• The receiving server has explicitly blocked your sender

Hard bounces should be treated as permanent. You should immediately remove hard-bounced addresses from your sending lists. Continuing to send to known-bad addresses is one of the fastest ways to damage your sender reputation.

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Soft bounces

A soft bounce is a temporary delivery failure. The address is valid, but delivery failed at the time of sending. Common causes include:

• The recipient’s mailbox is full
• The receiving mail server is temporarily unavailable or throttling inbound mail
• The message was too large to be accepted

Soft bounces may resolve on their own. However, if an address soft bounces repeatedly over time, treat it the same as a hard bounce and stop sending to it.

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How to minimize bounces

Keeping your bounce rate low is critical to maintaining deliverability. Here are the most effective practices: Keep your list clean

• Remove hard-bounced addresses immediately after a bounce event
• Regularly prune addresses that have not engaged in a long time
• Use double opt-in for new subscribers to verify addresses before adding them to your list

Validate addresses before sending

• Use an email validation service at the point of address capture to catch obvious typos and fake addresses
• Avoid purchasing third-party email lists — they tend to be full of stale and invalid addresses

Warm up new sending infrastructure gradually

• If you’re starting to send from a new domain or IP, ramp up volume slowly
• Sudden spikes in volume from a cold sender look suspicious to receiving servers and can result in temporary rejections (soft bounces)

Monitor and act on alerts

• Helo will surface bounce rate warnings before they become critical — check your channel health regularly and investigate spikes as soon as they appear
• Use the Webhooks feature to receive real-time bounced events so you can update your list immediately without polling

Use a Sandbox Channel during development

• Test your integration with a Sandbox Channel to avoid accidentally sending to real addresses during development, which can contaminate your bounce metrics from day one

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Simulating bounces

TODO