Sending behavior

Give each mailbox a human workday: randomized hours, volume, lunch break, and spacing, in its own timezone.

Automated sending looks automated. A mailbox that sends exactly 40 emails every day, starts at 09:00:00, and spaces every send exactly 600 seconds apart is describing itself as a machine in its own headers.

Sending behavior fixes that. You give a mailbox ranges instead of fixed values, and it rolls one workday out of those ranges each day: a start time, a finish time, a lunch break, a daily target, an hourly ceiling. It then keeps to that day.

Everything here is per mailbox and lives in its own timezone, so a London mailbox and a Denver mailbox on the same campaign each keep their own office hours.

Turn it on

Mailboxes > pick a mailbox > Sending > Sending like a person.

It is off by default. A mailbox that has not opted in keeps its fixed daily cap and minimum gap exactly as before, so switching this on is the only thing that changes its behavior.

While it is off, the rest of the tab is greyed out and read-only, because none of it applies. Turn the switch on to edit the ranges.

What gets randomized

Setting	Default range	What it controls
Working days	Mon-Fri	Days this mailbox sends anything at all, cold and warmup alike
Workday start	`09:03` to `09:27`	The mailbox opens at a different minute each day
Workday finish	`17:18` to `17:56`	Nothing is scheduled after the day's rolled finish
Lunch break	starts `12:00`-`13:30`, lasts `30`-`60` min	A quiet gap in the middle of the day
Cold emails per day	`30` to `45`	The day's cold-send target
Cold emails per hour	`5` to `9`	Stops the whole day landing in one burst
Delay between emails	`90` to `420` seconds	Drawn fresh for every send

Every time is local to the mailbox's own timezone, which you set on the mailbox itself.

A new mailbox has no timezone set, and that is a valid state rather than a gap: with none set, only the campaign's own sending window applies. Set one when the mailbox belongs to somebody in a particular place, and both calendars then have to agree before a send goes out.

The daily plan

The roll happens once per mailbox per local day, and the result is stored. That matters: the scheduler recomputes a mailbox's next slot many times a day, and a fresh random workday on every calculation would mean the mailbox never actually keeps to one.

The Sending tab shows today's rolled workday at the top: the hours, the break, the spacing band, the hourly ceiling, and how much of the day's target is already spent. That is the answer to "why is nothing sending right now".

Only emails that actually went out count against the day's target. A campaign wakes itself up far more often than it sends, and most of those wake-ups find nothing to do: every mailbox is mid-gap, the workday has not opened yet, or no contact is due. Those are not sends. They do not show up in the count, they do not spend the plan, and neither does the run the campaign has queued next.

Editing the ranges does not change today. Today keeps the workday it already started, and the new ranges take effect on the next roll.

How it interacts with your other limits

Sending behavior can only ever lower volume or delay a send. It can never raise a mailbox above its own daily cap or bring a send forward.

The day's rolled target is applied as a minimum against the mailbox's daily cap and the campaign's daily limit. If the mailbox is capped at 50 and the day rolls 38, the day is 38.
The delay range replaces the mailbox's fixed minimum gap while behavior is on.
A campaign's own sending windows still apply. A send has to satisfy both calendars: the campaign's window in the campaign timezone, and the mailbox's workday in the mailbox timezone.
Warmup follows the same working days, hours, and break, so warmup mail is not arriving at 03:00 from a mailbox whose campaign mail keeps office hours. Warmup is not charged against the cold daily or hourly ceilings; it has its own ramp.
Smart send for your own replies follows the workday but is never charged against the cold budgets.

The hourly ceiling is doing real work

Without it, a mailbox with a 40/day target and a 90-second floor could empty its whole day before 11am and then sit silent. That is a more obvious pattern than sending too much.

Choosing ranges

The defaults describe an ordinary weekday sender and are a good starting point for most mailboxes. If you change them:

Keep the daily range inside the safe cold band. 30-50/day is normal for a warmed mailbox; a mailbox connected in the last month should stay nearer 10-20/day.
Keep the delay range wide. A narrow range is only slightly less of a pattern than a fixed value.
Leave the lunch break on. It is one of the cheapest signals of a real person's inbox.
Do not set the workday to cover the whole clock. A mailbox that sends at every hour of the day is not describing an office.

The break has to fit inside the shortest workday the ranges can produce, and the latest possible start has to come before the earliest possible finish. The editor blocks a save that would break either rule.

Sending in the recipient's timezone

Sending behavior places a send inside the mailbox's day. Send-time optimization places it inside the recipient's day: hold each campaign email until the clock where the recipient reads mail reaches an hour you chose.

Settings > Sending > Send-time optimization. It is off by default, so nothing about your current sending changes until you turn it on.

Setting	What it does
Use the recipient's local hours	The switch for the whole feature
Read each contact's timezone	Uses the contact's `timezone` field first, then the country its email domain points at
Fallback timezone	Used when a contact's timezone cannot be worked out
Skip weekends	Pushes a Saturday or Sunday send to the next weekday
Delivery hours	The local hours a send is allowed to land in

SendSets works out the recipient's timezone in this order:

The contact's timezone custom field, when it holds a valid IANA name such as America/Denver.
The country implied by the email domain's country-code suffix: acme.de is read as Berlin, acme.co.uk as London. Generic domains like .com and .io carry no location, so they fall through.
The fallback timezone you set.

It only ever delays a send

Send-time optimization can move a send later, never earlier. Every other constraint still binds: the campaign's own sending window, the mailbox's workday and daily cap, the minimum gap between sends. If the recipient's hours and the mailbox's hours never overlap, the send goes out at the next moment both calendars allow rather than not at all. It will also never push a send past the campaign's end date.

Because it delays sends, a campaign with tight delivery hours and a small mailbox pool sends fewer emails per day than one without. Widen the hours if throughput matters more than placement.

API

The profile and today's plan are both readable and writable through the API. See Endpoints for the scopes.

GET  /api/v1/emails/{id}/behavior
PUT  /api/v1/emails/{id}/behavior
GET  /api/v1/emails/{id}/behavior/plan

PUT is a partial update: send only the fields you want to change. It is naturally idempotent, so retries are safe without an Idempotency-Key.