Bounce protection
Sending providers watch how many of your emails bounce. Amazon SES, for example, starts reviewing an account at about 5% bounces and can shut sending down entirely well before 10%. A bounce is an email to an address that doesn't exist or won't accept you — and cold or scraped lists are full of them. SubsiMail measures your real bounce rate and steps in early, long before your provider would.
SubsiMail can only protect you from bounces it can see. Make sure at least one of the two collection methods below is set up — the Accounts page shows a warning under any mailbox where bounces aren't being collected.
How bounces are collected
| From an inbox | When an email can't be delivered, the receiving server sends a “delivery status” notice back. SubsiMail reads these in every mailbox connected with IMAP, every 5 minutes, together with spam-complaint reports. Only permanent failures count (a dead address); a full mailbox or a temporary delay does not. |
| From Amazon SES directly | SES doesn't email you its bounces; it publishes them to Amazon SNS. Settings → Bounce & complaint feed gives you a private address to give SNS — see Amazon SES. |
The moment a bounce is recorded, that address is blocked in every campaign and mailbox (it joins the suppression list), and its sequence stops. It is never mailed again.
What SubsiMail does, and when
| Level | When | What happens |
|---|---|---|
| Warning | 1% or more of a campaign's recent emails bounced (after at least 20 sends) | A note on the campaign page. Nothing pauses. |
| Checkpoint | More than 2% of the campaign's last 100 emails bounced (after at least 50), or 10 of them, or spam complaints above 0.3% | The campaign pauses and asks you whether the list is clean. |
| Mailbox ceiling | More than 4% of a mailbox's emails bounced over 48 hours, across every campaign on it | Every campaign on that mailbox pauses. This can't be overridden with a click. |
Rates are measured on emails that have had at least 15 minutes for a bounce to come back, so a fresh send doesn't look cleaner than it is. A banner on every page tells you when anything has paused because of bounces.
When a campaign pauses at a checkpoint
The campaign page shows the real numbers (“3 of the last 100 emails bounced”), a link to the addresses that bounced, and your choices:
- The list is clean — continue. The campaign resumes and measures bounces afresh. The mailbox restarts at a reduced daily limit (150 a day) and builds back up. You can do this once: if the same campaign stops again within 7 days, the shortcut is gone.
- Continue slowly (after you've cleaned the list). You tick a box to confirm you removed or verified the risky addresses; the mailbox restarts at 50 a day.
- Stop this campaign. It stays paused until you resume it yourself.
The ordinary Resume button doesn't work on a campaign paused for bounces — the question has to be answered first. While the mailbox is over its 4% limit, nothing on it can resume; that clears by itself within 48 hours of the last bounce.
The test batch
A campaign that has never sent sends only its first 50 emails, then waits for their bounces to come back before releasing the rest: about 2 hours for a normal campaign and 30 minutes for a promotion. If the test batch bounces badly, the checkpoint pauses the campaign with most of your list untouched. Campaigns with fewer than 50 contacts are simply sent. Follow-up steps are never held back by this.
Ramp-up for new mailboxes
A mailbox connected from this version on starts at a small daily limit that grows over two weeks: 50, 75, 100, 150, 200, 300, 400, then 500 a day, and then no ramp limit. Your own daily limit still applies on top. The Accounts page shows “Ramp-up: at most N emails today”, and the sending calendar forecasts with it. Mailboxes that already existed when you upgraded are not ramped; a mailbox restarted after a bounce pause is.
The list check
Before you activate a campaign, its Launch tab looks at the audience and warns you when it stands out: a large share of role addresses (info@, sales@, support@ …) which bounce and complain far more often, addresses at throw-away email services, and addresses that are already blocked and will be skipped. It's advice, not a gate — but a list that triggers it deserves a run through an email-verification service first.
What it can't do
- It can't see bounces nobody tells it about — hence the two collection methods above.
- It can't undo a shutdown. Your provider's limits are theirs; SubsiMail's job is to stop you approaching them.
- Corporate mail servers sometimes reject cold email from unknown senders by policy. Those rejections count as bounces too, so a list of large companies bounces more than a list of small businesses.