If a recipient sees an email arrive from a different address or domain than the one you sent from, there are two very different explanations. This guide helps you tell them apart. (For the full explanation of how rotation works and why we recommend it, see Why does the recipient see a different sender or domain? (mailbox rotation).)
This is usually expected: mailbox rotation
To protect mailbox health, Maildoso automatically rotates and filters sending behind the scenes. Because of this, a recipient may occasionally see a different one of your domains than expected. This is intentional, and nothing changes operationally for you. (When using a single domain on your Maildoso account, mailbox rotation is not possible due to the absence of additional domains for rotation, so the recipient-visible "From" and reply addresses remain fixed.)
The recipient still receives the email normally.
If they reply, the reply is automatically routed back to the original mailbox that sent it.
Only the first email in a thread can come from another mailbox. Follow-ups always go out from the original mailbox.
Rotation only uses mailboxes in the same rotation group on your own account (grouped by redirect URL, Master Inbox forwarding address and mailbox names).
You don't need to do anything — this is part of how we keep your mailboxes healthy over time.
How to recognise it in the headers: the From address, Return-Path and DKIM signature (d=) belong to another of your domains, while the Message-ID usually still shows the domain you sent from. If you're searching your inbox for a test message, search by subject rather than by the original From address.
Why rotation is on by default
Rotation exists to keep your campaigns healthy without manual work. When a mailbox starts losing reputation, our system shifts cold sending to healthy mailboxes in the same group and lets the weakened one rest until it recovers — you don't have to pause campaigns or replace domains. It has run on all Maildoso accounts since mid-2025, and in our measurements most senders whose inbox placement had dropped below 50% recovered within about two weeks with rotation on.
If you'd rather not have rotation: we can switch it off
Rotation is an account setting, not a fixed part of the product. If your use case needs the visible sender to always match the mailbox you sent from (for example a fixed sender identity, deliverability tests you're running per domain, your own per-domain rotation logic, or a compliance requirement), contact us and we'll disable rotation for your account — it takes a few minutes. We generally recommend keeping it on for deliverability, but the choice is yours, and it can be turned back on later. Keep in mind that with rotation off, mailboxes that lose reputation no longer recover automatically, so you'll need to monitor and rest them yourself. Note that turning rotation off doesn't give you a fixed sending IP or PTR record; those are managed on the shared pool for every account.
If you only need to keep some domains apart (for example, different clients), you don't need to turn rotation off: give each group its own redirect URL, and domains in different groups won't rotate with each other.
Getting the most out of rotation
Rotation works best, and leans least on any single domain, when two things are set up on your account: a redirect URL on your domains, and your Master Inbox. Without them, rotation has less healthy capacity to work with and can lean harder on the domains that aren't fully configured. See Domain redirects: what they do and how to set your redirect URL and Using your Master Inbox and connecting mailboxes to an email app to check both are set up on your account. Additionally, consider adding multiple domains if mailbox rotation is a requirement for your email strategy.
When it's not just rotation
Occasionally what looks like a sending issue is actually something else, for example:
The sending address shown to the recipient consistently belongs to a domain that has nothing to do with your account or plan.
The message content itself looks altered in transit (for example, the sender address inside the body text doesn't match who actually sent it).
The mismatch happens the same way every time, for the same mailbox, rather than varying as you'd expect from rotation.
Mail sent from your mailboxes to your own other Maildoso mailboxes (or to your Master Inbox) never arrives after a rotation change — that's a forwarding/routing question for us, not rotation.
If any of that sounds like what you're seeing, it's worth having us take a look at your specific account rather than assuming it's rotation.
What to send us if you're not sure
To help us check quickly, include:
The mailbox address you sent (or authenticated) from.
The address the recipient actually saw as the sender.
A copy of the message headers if you have them, or a screenshot of the received email.
Still not sure whether this is expected behavior or something we need to fix? Contact us with the details above and we'll review your specific case.