Why is my broadcast taking days to send?

Because it is being paced on purpose. A broadcast sends from your own email account, a few seconds apart, up to a daily limit. A send larger than that limit continues automatically on the following days until everyone has been reached.

The screen tells you before you commit: if a broadcast will span more than one day, the first step says roughly how many days it will take.

Why the pacing exists. Mail providers judge a sending address by its behavior. An account that has been sending a handful of one to one emails a day and suddenly emits two thousand identical messages in ten minutes looks exactly like a compromised account, and the usual result is that the mail stops reaching inboxes, or that the account itself is restricted. Since broadcasts go out from your real address, the address at stake is the one you use for actual customer conversations. Spreading the send is what keeps it safe.

The limit applies per person, not per workspace, and it counts everything you have scheduled. If you start a second broadcast while the first is still going, the two share the same daily budget and the second is scheduled around the first rather than doubling your rate.

You do not need to keep the tab open. Sending continues on its own. Close Coastline, sign out, use your phone; it makes no difference. Progress is at Campaigns, Broadcasts (/campaigns/broadcasts), where each broadcast shows sent, failed, skipped and remaining, updating while it runs.

One thing to know before you start: a broadcast that is on its way cannot currently be stopped. Check your audience, your subject line and your links on the preview step, because once it is sent the remaining days will continue.

If a broadcast shows failures, the most common cause is a disconnected email account. Reconnect it at Settings and the remaining recipients resume. See how to connect your email inbox.