Email Marketing Software for Agencies: One Platform for Every Client
Cem Hurturk, Founder of Octeth
Updated First published
Agencies that run email for clients usually start the same way: each client gets its own Mailchimp or Klaviyo account, the agency logs in to all of them, and the client pays the vendor. It works for three clients. At fifteen, the agency is managing fifteen subscriptions, fifteen sets of billing and fifteen vendor relationships it does not own.
I have spent most of my career building email software for exactly this situation. Octeth was designed so that one agency can run every client from one platform, under its own brand. This page compares the main options for agencies, with facts checked on the vendors' own pages on 2026-10-03.
Short answer
| If you want | Look at |
|---|---|
| To stay on the tools your ecommerce clients already use | Klaviyo or Mailchimp agency programs (client pays, you earn a commission) |
| A hosted platform with client sub-accounts and your own branding | Campaign Monitor (agency accounts, private labeling) |
| One platform for all clients, under your brand, with no per-client fees | Octeth (self-hosted), or a reseller platform such as MailWizz or Acelle Mail |
| A hosted reseller platform without running servers | BigMailer, Simvoly, Transpond |
| Email inside a full CRM partnership | HubSpot Solutions Partner Program |
What agencies need from an email platform
- One login for every client, without switching accounts all day.
- Separate data per client: lists, templates, automations and reports that never mix.
- Client access with limits, so a client can see reports without editing automations.
- Billing you control: either you bill the client and keep the margin, or the vendor bills with your markup.
- Deliverability isolation, so one client's bad list cannot hurt the others.
- Your brand, if you sell email marketing as your own service.
- Costs that do not multiply with every client you sign.
Agency programs compared
From each vendor's partner pages, as of 2026-10-03:
| Platform | One login, many clients | Who pays the vendor | What the agency earns | White label |
|---|---|---|---|---|
| Octeth | Yes, client accounts on one installation | You buy one license, then bill clients yourself | Your full margin | Yes, full |
| Klaviyo | Yes, multi-account and Portfolio | The client (reselling is not allowed) | Referral, co-sell and management fees (rates not public) | No |
| Mailchimp | Yes, connected accounts | The client | 25% on new referrals, 5% on managed accounts, 12 to 36 months | No |
| Campaign Monitor | Yes, client sub-accounts | You, or the client with your markup | Your markup | Yes, logo, colors and domain |
| Brevo | Sub-accounts on Enterprise (from $2,499 a month) | One invoice or per sub-account | 10% to 25% commission on the partner program | No official offer |
| Omnisend | Via the partner portal | The client | 20% revenue share | No |
| MailerLite | Yes, account switching | Each account has its own plan and billing | Referral commission | No |
| HubSpot | Partner access to client portals | The client | 20% for 3 years, with a $400 a month membership | No |
| Constant Contact | Yes, partner portal | The client, or you on Single Bill | 18% for 2 years plus up to $200 per client, or an upfront discount | No |
The pattern is clear. With most mainstream platforms, the client pays the vendor and the agency earns a commission. The client relationship, the data and the account belong to the vendor. Campaign Monitor is the main hosted exception, with private labeling and agency markup. White-label reseller platforms and self-hosted licenses go further. Our white-label email marketing guide covers those in detail.
What per-client pricing costs an agency
On per-client platforms, every client needs its own paid plan. From the vendors' pricing pages on 2026-10-03:
| Plan, per client | 10,000 contacts | 50,000 contacts |
|---|---|---|
| Klaviyo Email | $150 a month | $720 a month |
| Mailchimp Standard | $135 a month | $450 a month |
| Campaign Monitor Lite (annual discount) | $105.30 a month | $357.30 a month |
For 10 clients with 10,000 contacts each, that is about $12,600 to $18,000 a year. At 50,000 contacts each, it is about $43,000 to $86,000 a year. It grows with every client you sign and every contact they add.
On a self-hosted platform, the license is paid once. Your running costs are servers and sending, for example $0.10 to $0.16 per 1,000 emails on Amazon SES. Client 50 costs the same in platform fees as client 10. Our cost comparison puts numbers on this for common platforms.
Deliverability: keep clients from hurting each other
When all your clients send through the same shared IPs and domains, they share one reputation. One client with a purchased list can push everyone else into spam. On per-client SaaS accounts the vendor's shared pools apply, and on most reseller platforms you cannot choose.
In Octeth, each client group gets its own delivery servers, assigned per channel (marketing, transactional, autoresponder). A new or risky client can send through its own relay account or IPs while the rest stay clean. Each client authenticates its own sender domains. Our free SPF generator, DKIM generator and DMARC generator make that quick, and the IP warm-up planner schedules new IPs. If you would rather not run sending yourself, we operate delivery for customers on dedicated IPs.
How agencies run clients on Octeth
- Your platform, your brand. Octeth runs on your domain with your logo, product name and colors. Your clients log in to your platform.
- One account per client. Each client gets its own lists, segments, templates, journeys, sender domains and reports. Clients never see each other.
- Client groups set limits, permissions, branding and delivery servers for a set of clients, for example a premium tier.
- Journeys with email and SMS steps, decision branches, waits and webhooks, built per client.
- Billing your way: invoice clients from your own system using Octeth's account usage API, or turn on the built-in subscription billing with Stripe or accept.blue.
- Installation, onboarding and support from the team that builds Octeth. A full multi-client setup takes two to four weeks.
Octeth has been in production since 1999, with 20,000+ installations in 138 countries. Paid licenses start at $5,500 one-time, and multi-client licenses are priced by the number of accounts. Octeth is not the right fit if you manage fewer than five clients or do not want to invest in setup. A per-client SaaS account or a hosted reseller platform will be simpler.
What agencies charge for email marketing
Published agency retainers for email marketing range from a few hundred dollars a month for starter packages to $2,500 to $10,000 or more for full-service programs. Campaign Monitor reports that agencies commonly mark up the platform by 25% to 50%, or charge $200 to $500 per client for it. These figures come from agencies and vendors, not an independent survey, so use them as a range rather than a benchmark. With per-client SaaS, the platform fee comes out of that retainer. With one platform for all clients, most of it stays with you.
Frequently asked questions
Can I manage all my clients from one login?
Yes, on most platforms. Klaviyo, Mailchimp, MailerLite and Constant Contact let you switch between client accounts. Campaign Monitor and Octeth go further, with client accounts inside one agency platform.
Does each client need its own paid plan?
On Klaviyo, Mailchimp, MailerLite, Omnisend and HubSpot, yes: each client account has its own plan. On a self-hosted platform such as Octeth, one license covers all client accounts within your tier.
Who pays the vendor, me or the client?
On most mainstream agency programs the client pays and you earn a commission. Campaign Monitor lets you pay or bill the client with your markup. With Octeth you pay for one license and bill clients however you like.
Can I white-label the platform with my logo and domain?
Among mainstream hosted tools, Campaign Monitor offers private labeling. Reseller platforms and self-hosted platforms such as Octeth offer full white-label, including your own domain and product name.
Can clients log in and see only what I allow?
Yes, on platforms with client permissions. Campaign Monitor and Octeth let you control what each client account can see and do.
Is each client's data kept separate?
On every platform here, client accounts have their own lists, templates and reports. On a self-hosted platform, all client data sits on your servers.
Does one client's bad list hurt the others?
It can when clients share sending IPs and domains. Platforms that let you assign delivery servers per client, such as Octeth, keep a risky client from affecting the rest.
What does it cost to switch clients from Mailchimp or Klaviyo?
The platform cost is mostly time: exporting lists and suppression data, rebuilding templates and automations, and authenticating sender domains. Plan for warm-up if sending moves to new IPs.
How much should I charge clients for email marketing?
Published ranges run from a few hundred dollars a month for starter packages to $2,500 to $10,000 or more for full service. Price your service on outcomes and workload, and keep the platform cost a small share of it.