Need more sending capacity? You can add extra mailboxes to your existing plan at any time. There are two steps: buy the add-on, then create the new mailboxes.
Google Workspace: new allotment isn't currently available to purchase, so the add-on flow below is for SMTP mailboxes; unused Google Workspace slots already on your plan can still be used in step 2. Current status: Google Workspace mailboxes.
How much do SMTP mailboxes cost?
SMTP mailbox pricing is volume-based: your total SMTP mailbox count sets the per-mailbox monthly rate for your whole account.
1–224 mailboxes: $2.50 / mailbox / month
225–924 mailboxes: $0.75 / mailbox / month
925+ mailboxes: $0.50 / mailbox / month
See How much do SMTP mailboxes cost? Volume pricing tiers for the full breakdown, including how the rate applies when an add-on purchase moves your account into a new tier.
1. Buy more mailboxes
In your dashboard, go to Billing → Packages & Add-ons (or buy through our website — if the two show different prices, the website is current; see Why is the price in the app different from the price on our website?).
Choose how many SMTP mailboxes you want to add.
Complete checkout. Your new mailbox allowance is added to your account right away.
Mailboxes can also be created programmatically via API or MCP once slots are purchased.
2. Create your new mailboxes
Go to Accounts → Add more email accounts.
Pick the mailbox type. SMTP is available to purchase now; Google Workspace can only be selected if you already have unused Google Workspace slots on your plan. Note that a single domain is used for one type only — either Google Workspace or SMTP, not both.
Enter the sender names and usernames for each mailbox, then choose the domain they should sit on.
Wait for the mailboxes to show as Active. This usually takes about 30 to 90 minutes.
In some cases, mailboxes may appear inactive while they are still being provisioned. This process is automatic, and no additional steps are required. Once provisioning is complete, the mailbox status will update to active.
If mailboxes remain inactive beyond 90 minutes, check the domain's status on the Domains page: mailboxes only activate once their domain is Active. For an external domain, check that the required Maildoso nameservers (NS) are correctly set at your registrar; for a domain registered through Maildoso, contact us with the domain name and we'll check provisioning.
If you need a custom number of mailboxes
Add-ons are sold in set bundle sizes (for example, a minimum of 10 at a time), so the dashboard may not let you buy an exact custom amount on its own. If you need a specific number of SMTP mailboxes, just contact us with your account email and the exact quantity you'd like, and we'll add that allowance to your account for you. If instead you need a different mix of mailboxes and domains altogether — not just more of the same — see Changing or switching your plan.
Adding more domains
If you also need more domains, you can purchase them from your dashboard the same way you did when you first set up your account. If you're not sure how many domains your new mailboxes need, contact us and we'll help you plan the right setup.
Still have questions about expanding your plan? Contact us and we'll be happy to help.