- 1
Scale with mailboxes, not with one inbox's limit
Total campaign volume comes from how many senders it uses. Adding mailboxes to the sender pool is the safe lever; pushing one mailbox past its daily limit is not.
- 2
Stand up more mailboxes
Add mailboxes — SMTP/IMAP one-by-one, or bulk-import a CSV — on fresh or aged sending domains. Spreading across more domains isolates risk further than piling more mailboxes onto one domain.
- 3
Authenticate every domain
For each sending domain, set up SPF, DKIM (Managed DKIM for credential mailboxes), DMARC, and a tracking domain. Un-authenticated volume gets filtered no matter how carefully you pace it.
- 4
Warm up new mailboxes first
Don't put real campaign load on a cold mailbox. Let warm-up build reputation; Auto-adjust keeps the daily limit in step with Sending health.
- 5
Set per-mailbox limits sensibly
Leave Auto-adjust on and add a Send ceiling you're comfortable with — the range is 20–500 per day per mailbox. Keep cold mailboxes low.
- 6
Build the campaign's sender pool
In the campaign's Email Accounts selector, add the warmed, authenticated mailboxes as senders — shown as “N/M selected.” Sending now spreads across all of them.
- 7
Arm Delivery Protection
Turn on auto-pause (bounce 5% / spam 0.1%) so a scaled campaign stops itself if reputation slips — essential once volume is high.
- 8
Ramp gradually and watch health
Add senders in waves, watch each mailbox's Sending health and the campaign's bounce/spam rates, and only widen the pool while the numbers stay clean.
Pro tips
Hard-won shortcuts that keep warm-up on track.
Volume = mailboxes × safe per-mailbox limit
To double sends, roughly double your warmed senders — never double one mailbox's daily limit past what's safe (500 is the hard per-mailbox ceiling).
Spread across domains, not just mailboxes
Ten mailboxes on one domain share that domain's reputation. Several domains isolate blast radius if one gets flagged.
Never add a cold mailbox straight to a live campaign
Warm it first; auto-adjust and warm-up exist precisely so you don't hand-tune a ramp.
Scaling without auto-pause is gambling
The one setting that saves you at volume is Delivery Protection — arm it on every campaign before you widen the sender pool.
Frequently asked questions
How do I send more emails per day?
Add more warmed, authenticated mailboxes to the campaign's sender pool. Volume scales with senders, not by raising one mailbox's limit.
Is there a mailbox rotation setting?
No — “rotation” just means selecting multiple sender mailboxes; FirstSales spreads sends across whichever ones you assign.
What's the per-mailbox limit?
20–500 emails/day, default 50, with Auto-adjust ramping it from Sending health. Scale by adding mailboxes, not by exceeding 500 on one.
Do I need to warm up every new mailbox?
Yes — a cold mailbox on real volume tanks deliverability. Warm it up first; auto-adjust respects warm-up health.
Does each domain need its own authentication?
Yes — SPF/DKIM/DMARC and a tracking domain per sending domain, or the extra volume just gets filtered.
How do I protect a high-volume campaign?
Arm Delivery Protection (auto-pause on bounce 5% / spam 0.1%) so it stops itself before reputation damage spreads.
Should I use one domain or several?
Several — spreading mailboxes across domains isolates the blast radius if one domain gets flagged.
How fast can I ramp?
In waves. Add senders gradually, watch each mailbox's Sending health and the campaign's bounce/spam rates, and widen only while metrics stay clean.
Ready to put this into practice?
Start your FirstSales trial and launch a warmed, authenticated mailbox in minutes.
Start for $1