Sending a Mailing

Send a Deliver mailing once or on a recurring basis. Select Send Mailing from the mailing overview page to open the sending options.

Before sending any mailing, you should:

• Run Check Logic in your Recipient List queries.

• Preview the message as it will appear on desktop and mobile.

• Preview the destinations of any links.

• Send a test message.

Pre-flight checks

Pre-flight checks appear at the top of the Send Mailing pop-up and flag common setup issues before you send. They can identify the most common mistakes in Deliver, but don’t rely on them alone for review.

Red errors prevent activation of the message, while orange warnings require a user to acknowledge the warning by typing a confirmation message.

For example:

• If the Recipient field is missing an email address, Slate displays an error and prevents sending the message.

• If the Recipient field has a static email address instead of a merge field, Slate displays a warning but lets the user send the message.

📖 See also: Deliver Pre-Flight Checks

Estimated Recipients

Slate displays a summary of the expected recipient count before the mailing sends.

Split Testing

If content exists in “version 2” of the mailing, Slate displays Split Testing options.

📖 See also: Split Testing (A/B Testing)

Recipient Lists

Slate displays the titles of recipient and suppression lists configured for the mailing.

Batch Size (optional)

Enter a batch size to limit the number of recipients for a single send. For example, if you enter 10, the mailing stops after sending to 10 random records.

Use a batch size to send to a set number of recipients per Delivery Window. Slate limits each Delivery Window to the number of records specified in the batch size field. The mailing remains in Scheduled/Running status. When the next delivery window runs, Slate sends the next batch of messages. 

Review

Select this option to mark the message as ready for review. It prevents the mailing from sending until cleared, and can flag messages for approval before sending.

Outbox

Send to Outbox and don’t deliver automatically. Users without the Send Mailing permission can send Deliver mailings to the Outbox for review and approval by users with the Send Mailing permission.

Frequency

Choose how often to send the mailing:

• Send mailing once

• Send mailing on a recurring basis

If you select Send mailing on a recurring basis, additional options appear:

• Date Range: Select the start and end dates for the mailing. Leave the end date empty to run the mailing until manually deactivated.

• Weekdays: Select the days of the week on which the mailing sends.

⚠️ Notes on recurring mailings

• Start date is inclusive, end date is exclusive: The sending range excludes the "until" date. For example, with a start date of 5/24/2023 and an end date of 06/30/2023, the mailing runs from May 24 through June 29, 2023—Slate sends no mailing on June 30.

• Recurring mailings must span at least 24 hours. To send over a shorter window, set Frequency to Send mailing once.

• Indefinite mailings require a query-based recipient list. Running a mailing with no end date isn't compatible with uploaded spreadsheet lists. To run an ongoing mailing, build the recipient list from a query.

Timing

Choose when Slate sends your mailing. Your options depend on the frequency you selected.

How scheduling works

🛑 Critical: you can't change a mailing once it's scheduled.

As soon as Slate finalizes the recipient list and schedules the messages, you can no longer cancel the mailing, edit it, or change who receives it. Double-check everything before scheduling.

When Slate finalizes the recipient list

• Scheduled 24+ hours in advance: Slate finalizes the recipient list early in the morning on the delivery day, as early as midnight Eastern Time.

• Scheduled less than 24 hours in advance: Slate finalizes the recipient list immediately.

How Slate determines each recipient’s time zone

Some options can deliver in each recipient's local time zone. Slate reads the geographic data from the recipient's rank 1 address to determine their time zone.

• The record has no address, or Slate can't determine the time zone: Slate sends the message in Eastern Time, immediately after finalizing the recipient list.

• The delivery time has already passed locally: Slate might delay delivery by up to 24 hours.

🛑 If Slate can’t determine a recipient’s time zone, it will send a message as early as 12:00 AM Eastern Time.

Sending texts or emails in the middle of the night can get your messages filtered or blocked by unhappy recipients. To avoid this, use recipient-time-zone delivery only for recipients who have a rank 1 address with a valid latitude and longitude. Add a subquery filter to your recipient list query that checks whether a latitude or longitude exists, as a proxy for available time zone data.

Send mailing once

Send now

Slate finalizes the recipient list immediately and sends messages right away.

Send at a future date/time

Choose a delivery date and time, then select a time zone option:

• Eastern Time: Slate finalizes the recipient list at (or shortly after) your scheduled time and sends messages immediately to all recipients.

• Recipient’s time zone: Slate finalizes the recipient list early on the scheduled sending day, then delivers each message at your specified time in the recipient's local time zone. If you schedule the mailing 24+ hours in advance, finalization can begin as early as midnight Eastern Time.

Send mailing on a recurring basis

Send at a specific time

Choose a delivery time and select a time zone option. The mailing will repeat daily until you stop it or it reaches the stop date.

• Eastern Time: Slate generates a fresh recipient list each day and sends all messages at your chosen time.

• Recipient’s time zone: Slate generates a fresh recipient list each day and delivers each message at your chosen time in the recipient's local time zone.

Send during a delivery window

Choose at least two delivery windows. Slate generates the recipient list for each window and sends the mailing during the selected windows.

• Overnight: 2:00 AM to 4:00 AM

• Morning: 10:00 AM to 12:00 PM

• Midday: 12:00 PM to 2:00 PM

• Afternoon: 2:00 PM to 4:00 PM

• Evening: 8:00 PM to 10:00 PM

⭐ Best practice: Select at least two delivery windows.

If you select only one and a processing delay occurs during that window, the mailing might not send at all. Choosing multiple windows gives Slate a fallback.

Deduping

Deduping controls how Slate keeps the same person from receiving a mailing more than once. Deduping works at two levels. At the record level, a record receives the mailing only once. At the email address level, an inbox receives it only once, even when multiple records share that address.

This distinction matters when multiple records share the same email address. For example, if a family lists a parent's email on behalf of each student, Slate treats those as separate records but the same recipient.

📝 Recipients are email addresses, not records.

In the Deliver context, a “recipient” refers to a single email address, not a record.

You control both levels through three settings:

• Do not dedupe messages: No email-level check, but the record-level check still happens. Slate sends one message to each matching record. Multiple records sharing an email address each trigger a send.

• Send only one message/recipient: Adds an email-level check. Even if multiple records share an email address, Slate sends only one message to that inbox.

• Allow recurring delivery: Relaxes record-level deduplication so the same record can receive the mailing again after a minimum time you define.

Do not dedupe messages

Slate sends the mailing to a record if:

• The record satisfies the filter criteria.

• The record has not previously received the mailing.

Slate doesn't do an email-level check. If multiple records share an email address, each record receives a message.

⚠️ “Do not dedupe” refers only to recipient email addresses.

Slate still applies a record-level check, and sends the same message only once per record.

Send only one message/recipient

Slate sends the mailing to a record if:

• The record satisfies the filter criteria.

• The record has not previously received the mailing.

• The email address has not previously received this mailing.

Slate sends only one message per email address. If multiple records share an email address, whether in the same recipient list run or a previous one, only the first matching record receives the message. Slate skips additional records with that address.

Allow recurring delivery

Slate can send the mailing to the same record multiple times. It retains send history for each record during the frequency window. Once a record's most recent send is older than the specified frequency, Slate clears that history and the record becomes eligible to receive the mailing again.

Select a frequency to define the minimum time between sends to the same record. For example, you can send every 1 day, 2 days, or 30 days.

Slate sends the mailing to a record if:

• The record satisfies the filter criteria.

• The record has not previously received the mailing, or it was last sent the mailing at least x days ago, where x is the specified frequency.

Send mailing

Activates the mailing.

📝 Test environments can’t send messages.

In Test, Clean Slate, and Time Warp environments, Slate never actually sends emails or texts to recipients. Messages sent using the “send now” setting will appear on records' Timelines as if Slate had delivered them.

Scheduled mailings don't run automatically in these environments, so they don't appear as sent at all. Test recurring mailings in a Production environment with test records to confirm they send as expected.

Save settings

Saves your settings without sending the mailing.