For an existing website, assess Fastmail's MX-only route, prepare all addresses before cutover and verify both inbound and outbound mail. Keep transactional website sending on a service that permits it.
A custom email address can stay with your business when your website host or email provider changes. Fastmail supports that separation: you can keep your existing domain and website, then connect the email service through DNS. The useful part is control over your address, rather than having to move everything to one supplier.
This guide covers a small business moving ordinary person-to-person email to Fastmail while keeping a working website. It draws on official documentation checked on 13 October 2026. The example business and test plan are illustrative; we have not changed your DNS, tested your mailbox or measured delivery rates.
Decide what you are moving
Imagine a fictional design studio using example.com for its website and hello@example.com for enquiries. Its domain registration, DNS hosting, website hosting and email hosting are four different jobs. One company may currently provide several, but moving email does not automatically require moving the others.
For an existing website, Fastmail documents an MX-only setup: keep authoritative DNS elsewhere and point mail delivery to Fastmail. Its alternative is to host DNS with Fastmail. Do not change nameservers casually when a website already depends on the current zone. Custom domains require at least one account administrator on a non-Basic subscription. Check that requirement before buying a plan. See the custom-domain options.
Our recommendation for this studio is to keep its current DNS arrangement during the email move. This reduces the number of systems changing at once; it is an operational choice, not a claim that another arrangement is inherently unreliable.
A different starting point can be better for a new domain with no existing website or services: letting the email provider manage DNS may remove some manual setup work. For an established domain with several services and a DNS administrator, retaining that administrator’s current zone may be simpler to maintain. Choose from the actual dependencies, rather than assuming one DNS location suits everyone.
Make an address inventory before editing DNS
Write down every address that must continue working, including ones hidden in invoices, account recovery settings and contact pages. Record its owner and whether the address receives mail, sends mail, or does both. Use this working table before creating anything:
| Illustrative address | What it needs | Suggested starting point |
|---|---|---|
| owner@example.com | Private login, mailbox and recovery settings | Individual user |
| hello@example.com | Another public address for that same owner | Alias delivering to the owner |
| bookkeeper@example.com | Separate person’s access and messages | Separate user, with agreed permissions |
| orders@example.com | Human replies about purchases | Address with a named operator |
| Automated order receipts | Programmatically generated outbound email | Separate transactional email service |
An alias is an additional address delivering into an existing account; a user has a separate login, mailbox and storage quota. Four public addresses therefore do not necessarily mean four people or four user accounts. Conversely, an alias does not create a private mailbox for a colleague. Fastmail explains the distinction in addresses versus users.
Add two other columns to your inventory: “last verified” and “where published.” They make it easier to identify an old address that still appears on a PDF, or a supplier account that must not lose its password-reset route during the move.
Prepare the new mailboxes while the old service still receives mail
Fastmail’s business-migration guide starts by adding the domain, creating users and adding extra addresses while the existing MX records still point to the previous host. That gives you a prepared destination before the cutover. Importing old messages and routing new messages are separate tasks. Mail downloaded only to a desktop through POP may need a manual transfer. See the business migration procedure.
Keep access to the previous service while you reconcile both sides. An empty new mailbox may simply mean history has not been imported; an old inbox receiving a fresh message may mean a sender still has cached DNS information. Neither observation alone tells you to delete an account or change MX records again.
Choose a quiet period and designate one person to make the DNS change. Save an export or accurate record of the original zone and mail-routing settings, without copying passwords into the checklist. Define a rollback decision in advance: who can restore the previous mail configuration if critical addresses fail, and how will they preserve messages received on either service?
Use the domain wizard, with the website answer correct
Open Settings → Domains, add a domain you already own and follow Fastmail’s domain setup wizard. Confirm the registrar it identifies and answer Yes when asked whether the domain has a website that must remain available. The individual-address route is useful when you need multiple people or explicitly managed addresses; express setup targets simpler arrangements. The wizard supplies instructions for the situation you select. See the setup-wizard guide.
Before applying those instructions, identify the service that actually hosts your DNS. It can differ from the company where you renew the domain. If you are editing a zone that is not authoritative, a perfectly typed record may have no effect on the public domain.
Change email records, and preserve the website records
For the standard MX-only route, Fastmail lists in1-smtp.messagingengine.com at priority 10 and in2-smtp.messagingengine.com at priority 20, as the domain’s only two MX records. Follow the current account instructions if they specify a regional setup instead. Add the supplied authentication records too. Fastmail’s domain screen checks the resulting configuration. See the MX-only instructions.
Do not retain the previous provider as an extra MX target simply as an improvised migration backup. That is different from keeping access to the old mailbox. Also leave unrelated website A, AAAA and CNAME records intact: the change should not replace the web server’s address with an email server’s address.
Fastmail’s advanced DNS reference includes optional website and subdomain features as well as mail records. Copying its entire table would apply services you may not want. For DKIM it documents three CNAME selectors; use all the required records for your actual domain. If DNS is on Cloudflare, Fastmail’s MX-only guide says the relevant CNAME entries must be DNS-only, rather than proxied. See the manual DNS reference.
Understand SPF, DKIM and DMARC before replacing an existing policy
SPF identifies permitted sending systems for a domain used in mail delivery. DKIM signs parts of a message; DMARC checks alignment with the visible From domain and specifies a policy for failures. These mechanisms help receivers assess authenticity. They do not guarantee inbox placement or prove that every authenticated message is honest. Fastmail explains their roles and forwarding limitations in its sender-authentication guide.
List all legitimate outbound senders before updating SPF: perhaps the human mailbox service plus a separate newsletter or transactional provider. Fastmail warns that multiple TXT records beginning with v=spf1 cause detection problems. You need a coherent single SPF policy for the same domain, not another competing record each time you add a service. Do not remove a working provider’s authorization until you have deliberately retired it.
Likewise, preserve and review an existing DMARC policy instead of replacing it blindly with a sample. A policy used by an established website may cover more than the new mailbox. If you do not understand the current senders or policy, get the DNS administrator involved before enforcement changes.
Test receiving and sending as separate workflows
A successful login proves access to the account. It does not prove that outside senders reach your domain, that every alias exists or that your reply uses the right identity. Use a small evidence sheet like this:
| Check | How to check it | What success demonstrates |
|---|---|---|
| Main mailbox | Send a unique test message from an unrelated provider | That address receives external mail |
| Public alias | Repeat for hello@ and other published addresses | Each address reaches its intended operator |
| Outbound identity | Compose a new message from each public address | Recipient sees the intended From name and address |
| Reply route | Reply from the recipient account | The response returns to the correct mailbox |
| Authentication | Inspect received message headers and domain status | The particular message’s authentication results |
| Website | Load apex, www and a key page independently | The web routes still reach the intended site |
Record actual results and times. Check Spam as well as Inbox, and distinguish a bounce from a message filed in an unexpected folder. Use new subjects for each test so a conversation view does not conceal where the latest copy arrived. Do not send test campaigns to customers.
Keep website-generated mail on the right service
Fastmail is appropriate to assess for human correspondence such as discussing a project or replying to an enquiry. Its current terms prohibit using the service to send programmatically generated email outside the customer account; it is not a transactional sending platform. Do not configure a shop, password-reset system or contact-form auto-responder to send through Fastmail on that assumption. See the service terms.
You can keep a human contact address while choosing a separate permitted sender for the website’s generated messages. Test those messages separately after any SPF or DMARC adjustment. An email-hosting move is a good moment to find hidden dependencies, not a reason to put every type of sending through the same mailbox.
Choose it for the workflow you need
The strong fit here is a business that wants its own address, a focused email service and room to organise several identities without tying them to its website hosting. The separate-domain model also lets you retain the address during a future provider move, provided you keep the domain and configure the replacement correctly.
Before choosing, confirm the current plan’s custom-domain eligibility, user requirements and import route. If you chiefly need bulk campaigns, automated receipts or a large support queue with ticket assignment, evaluate services designed for those tasks instead. For day-to-day role addresses after setup, use our alias and rules workflow; for the broader buying decision, see business email for small teams.
There is also a case for keeping an existing email service: if it already meets your mailbox, collaboration and administration needs, owning a custom domain alone is not a reason to migrate. Check whether that service can host the address you need, and compare the full workflow before taking on a cutover. Fastmail becomes the useful candidate when its focused email approach solves a specific problem for your team.
Pagember participates in Fastmail’s affiliate program and may earn a commission from qualifying purchases through our Fastmail links.
The subscription check for this move
- One standalone domain mailbox: begin with Standard for domain use and third-party mail apps.
- A mixed business account: Basic can use a shared domain when an eligible administrator has a non-Basic plan. Basic keeps its other limits.
- Website-generated messages: keep a permitted transactional sender separate.
Check the current subscription guide before creating users. Existing customers should inspect their entitlement first. This move does not require buying another hosting package.
Sources and verification
Editorial review 2026-10-19. Source check dates are recorded separately. Notes describe what each source supports and its limits.
View sources
- Fastmail: custom domainsChecked Custom domains require at least one non-Basic administrator; DNS-hosting and MX-only options; ownership permits retaining an address across provider changes.
Limits: No plan purchase, particular account eligibility, DNS change or seamless migration is claimed. A new provider still requires correct configuration. - Fastmail: addresses versus usersChecked Aliases deliver to an existing account; users have separate logins, mailboxes and storage quotas.
Limits: No fixed alias allowance, numerical price or assumption that aliases provide private team mailboxes. - Fastmail: business email migrationChecked Prepare domain/users/additional addresses while old MX remains; history import differs from routing; desktop POP-only mail can need manual transfer; temporary old-provider delivery remains possible.
Limits: No fixed propagation or import completion time promised; no account or mailbox migration performed. - Fastmail: domain setup wizardChecked Domain wizard checks registrar, asks whether a website must remain online and offers express versus individual-address setup.
Limits: The reader must identify the authoritative DNS service and use instructions matching the real account. Registrar ownership does not prove DNS is hosted there. - Fastmail: MX-only setupChecked Standard two MX destinations and priorities; current domain instructions and regional alternative; authentication entries; single SPF policy warning; DNS-only Cloudflare CNAME instruction.
Limits: Only standard MX values are printed. No universal TXT policy, blind replacement of DMARC or guarantee of propagation/inbox delivery. Existing DNS and other legitimate senders must be preserved. - Fastmail: manual DNS configurationChecked Reference includes optional web hosting and mail services; three current DKIM CNAME selectors; warning that incorrect DNS can break website or mail.
Limits: Full reference table is not a setup script; optional web records are not copied into an existing website configuration. - Fastmail: sender authenticationChecked SPF authorised sending systems, DKIM signature purpose, DMARC alignment and policy, forwarding caveats.
Limits: Authentication is not an inbox guarantee or proof that a message is safe. Reader-specific headers and policy were not inspected. - Fastmail: current service termsChecked Terms effective 2 July 2026 prohibit programmatically generated outbound mail outside the customer account and describe service as human email communication.
Limits: This is operational product-fit guidance, not legal advice or affiliate content approval. No automated customer sending is recommended. - Fastmail plan selectionChecked Personal Individual/Duo/Family with Standard-level features; Business mix-and-match Basic/Standard/Professional and storage/app boundaries.
Limits: Duo two users, Family three-to-six; personal family pricing is not a business seat quote.