Agencies running outreach for a handful of clients can get away with almost any structure. Folders, tags, a naming convention, some shared infrastructure.
Around twelve clients it stops working, and the failure is not gradual. Somebody sends to the wrong list, a deliverability problem crosses between clients, an offboarding takes three days because nobody knows which domains belong to whom.
The structure that survives is not complicated. It just has to be decided before you need it.
The one rule everything follows from
One workspace per client. Never share infrastructure.
Not folders within a shared workspace. Not tags. A genuinely separate workspace with its own data, domains, IPs, suppression list and billing.
The reason is blast radius. If Client A’s aggressive list damages a shared sending reputation, Client B’s placement falls and you cannot explain why without breaching confidentiality. That conversation ends relationships, and it is entirely preventable.
Separation also makes offboarding a transfer rather than an extraction, which matters more than it sounds.
What lives at each level
Workspace (per client)
- Domains and mailboxes
- IP allocation
- Lead lists and campaigns
- Suppression and do-not-contact lists
- Unified inbox and pipeline
- Billing
Agency level (across all clients)
- Your own global do-not-contact list, applied everywhere
- Templates and sequence patterns you reuse
- Team access control
- Reporting that rolls up
The global do-not-contact list is the one exception to strict separation and it is important. If someone asks your agency to stop contacting them, that should apply across every client, not just the one that contacted them.
Naming conventions
Boring and load-bearing. Decide once and enforce.
Workspaces: ClientName — nothing else. Not Client Name - Active - 2026.
Domains: keep the client’s brand in the domain and your convention out of it. getnorthgate.com rather than northgate-agency-01.com. The prospect sees it.
Campaigns: ClientName_Segment_Channel_Month — for example Northgate_FinTechCFO_Multi_Sep. Sortable, searchable, and tells you what it is without opening it.
Lead lists: Source_Segment_Date. Knowing where a list came from six months later matters when something goes wrong with it.
Mailboxes: a consistent first-name pattern per client, matching real people where possible.
The test: can a new team member work out what something is from the name alone? If not, rename it now rather than at twenty clients.
Domains and IPs
Domains registered in the client’s name where possible, with delegated access to you. This is covered at length in the ownership piece and it is the single clause that determines how the relationship ends.
Some clients will not want to manage a registrar account. The workable compromise is registration in their name on an account you administer, with a written transfer clause.
Three mailboxes per domain, five maximum. Consistent across clients so capacity planning is predictable.
Separate IP allocation per client at meaningful volume. Below that, separate domains within a monitored pool is usually sufficient.
Never reuse a domain between clients. Obvious, and it happens when somebody offboards a client and recycles the warmed domains to save time. The reputation belongs to the previous client’s sending behaviour and the new client inherits it blind.
Access control
Three levels covers most agencies.
Agency admin. Full access across workspaces. Two or three people, no more.
Client manager. Full access to assigned workspaces only. Cannot see other clients exist.
Client user. Read access plus inbox to their own workspace, if you give clients logins. Under whitelabel, this is what they see.
The pattern to avoid is everyone having access to everything because it is easier. It is easier until somebody sends a campaign in the wrong workspace, which happens more often than anyone admits.
Onboarding checklist
Standardise it. Every new client, same sequence.
- Create the workspace, named to convention
- Register domains — client’s name, delegated access
- Configure DNS, verify records, start warmup
- Set up mailboxes at three per domain
- Load the client’s suppression list and their current customer list
- Apply your global do-not-contact list
- Assign the client manager, restrict everyone else
- Set daily send limits and sending windows
- Run an inbox placement test before the first campaign
- Document who owns what, in writing, where the client can see it
Point ten prevents most of the arguments that happen later.
Offboarding checklist
Equally standardised, and it is where reputations are made.
- Pause all campaigns
- Export lead data, suppression list and performance history
- Transfer domains — initiate early, they take five to seven days
- Export mailbox contents, or provide SMTP and IMAP credentials
- Hand over sequences and segment-level learnings, in a document
- Archive the workspace rather than deleting it
- Add their contacts to your global suppression list
A clean offboarding is worth more in referrals than the retainer was. An agency that hands over warmed domains and a documented set of learnings gets recommended; one that makes leaving difficult does not.
When it breaks
Shared suppression forgotten. A prospect asks Client A’s campaign to stop and hears from Client B two weeks later. Global do-not-contact list, applied everywhere.
Domain recycling. Covered above. Never.
Campaign sent in the wrong workspace. Access restriction prevents most of this.
Nobody knows who owns a domain. Document at onboarding.
One client’s volume affecting another. Only possible if infrastructure is shared. It should not be.
The short version
One workspace per client, never shared infrastructure, with your global do-not-contact list as the only thing that crosses boundaries.
Decide naming conventions before you need them, register domains in the client’s name with delegated access, and keep three mailboxes per domain consistently so capacity is predictable.
Restrict access so people see only their clients, and standardise onboarding and offboarding as checklists rather than habits.
None of this is difficult. It is just much harder to retrofit at twenty clients than to decide at five.
Next: lead generation for agencies, or white-labelling the stack.
Frequently asked questions
How should an agency structure outreach across multiple clients?
One workspace per client with separate domains, IPs, suppression lists and billing. Folders or tags within a shared workspace do not provide the isolation needed, because one client’s sending behaviour can then affect another’s placement.
Can agencies share sending infrastructure between clients?
They should not. A single client’s aggressive list damages everyone on the shared domains or IPs, and you cannot explain the cause to the affected client without breaching confidentiality.
Who should own the domains in an agency relationship?
The client, registered in their name, with delegated administrative access for the agency. This makes offboarding a transfer rather than a dispute and protects the warmed sending reputation.
What should an agency hand over when a client leaves?
Domains, mailbox access or exports, the lead list with enrichment, suppression and do-not-contact lists, sequences, and a written document of segment-level learnings.