How many senders to pick?
Last updated: December 5, 2025
Choosing the right number of senders is key to hitting volume targets quickly while protecting deliverability. The optimal count depends on two factors:
Your subscription tier (how many domains and mailboxes you have)
Whether you truly need separate sender identities for distinct campaigns
Higher tiers unlock additional domains and mailboxes, making it practical to expand sender count without throttling individual campaign volume.
1. Start with 1–2 Senders Across All Mailboxes
For the 1 000-email tier you receive:
Resource | Quantity |
Domains | 2 |
Workspaces per domain | 3 |
Total mailboxes | 6 |
Important: While you can add additional mailboxes later if your subscription has unused credits, it's recommended to request all the mailboxes you anticipate needing during initial setup. This allows all mailboxes to begin the warming process simultaneously, helping you reach target volumes faster. Adding mailboxes later means they start warming from zero while existing mailboxes are already ramped up. Note that higher tiers unlock additional domains and mailboxes, making it practical to expand sender count without throttling individual campaign volume. If you need more sending capacity beyond your current tier, you can purchase an additional domain (3 mailboxes) for $99/month or upgrade your subscription tier.
Assigning one or two senders to all six mailboxes is the best practice unless you have clearly different personas or territories that require their own signature.
Why not six senders (one per mailbox)?
Issue | Impact |
Warm-up caps | Each new mailbox starts at ~5 emails/mailbox and ramps to ~25 emails/mailbox over four weeks. If every mailbox has its own sender and campaign, each campaign remains low-volume for weeks. Adding mailboxes later means they start warming from zero while existing mailboxes are already ramped up. |
Fragmented data | Six separate send streams make it harder to see clear performance trends. |
Management overhead | More signatures, more replies, and more deliverability points to monitor. |
Important limitation: Active mailboxes cannot be renamed once they're being used in campaigns, as this would require deleting and recreating them, resulting in lost conversations and restarting the warm-up process from zero.
Consolidating on 1–2 senders lets all six mailboxes warm in parallel, so you reach meaningful daily volume sooner (up to ~30 emails/mailbox per sender after warm-up).