How Agencies Should Set Up Cold Email Infrastructure at Scale

Running cold email infrastructure for one brand is straightforward. Doing it for 10, 20, or 50 clients? That requires systems and structure. Here's how successful agencies do it.

Client Isolation

Never share domains or mailboxes across clients. If one client's sending practices get a domain flagged, you don't want it affecting other clients. Each client should have their own dedicated domains and mailboxes.

Domain Strategy Per Client

For each client, set up domains that are variations of their brand. A typical setup:

• Small client (500 emails/day): 4 domains, 12 mailboxes
• Medium client (1,000 emails/day): 7 domains, 20 mailboxes
• Large client (2,000+ emails/day): 14+ domains, 40+ mailboxes

Provider Mix

Use a mix of Google Workspace and Microsoft 365 for each client. This provides IP diversity and better coverage across different recipient mail servers.

Centralized Management

You need a single dashboard to manage all clients' infrastructure. Switching between multiple admin panels wastes hours every week. StackMail's workspace feature lets you organize everything by client.

Automated DNS

Manual DNS configuration doesn't scale. When you're setting up 20 domains for a new client, you need automated SPF, DKIM, and DMARC configuration. One-click setup saves agencies dozens of hours per month.

Credential Export

Your clients likely use different sequencers. You need to be able to export credentials in the right format for each platform. Bulk CSV export is essential.

Monitoring

Set up monitoring for all domains and mailboxes. You need to know immediately if a domain gets blacklisted or a mailbox gets suspended. Proactive monitoring prevents client churn.