MX record conflicts
Fix a 409 mx_conflict when you turn on receiving, and see why the sending MX record cannot collide with your Google Workspace or Microsoft 365 records.
Receiving mail
Receiving is the one case where Mailfully asks for an MX record on the domain name itself. Turning it on for mail.acme.com returns mail.acme.com MX 10 inbound-smtp.us-east-1.amazonaws.com, and that record does compete with any other MX on the same name.
If the name already has an MX record for another provider, turning receiving on fails with 409 mx_conflict and nothing changes. Leave the existing record alone and receive on a subdomain that has no mail of its own, such as inbound.acme.com: add it as a new domain, verify it, and turn receiving on there. Your Google Workspace or Microsoft 365 mail at acme.com keeps flowing.
Sending does not conflict
Mailfully's sending MX record goes on send.mail.acme.com, not your apex. MX records are looked up per name, so it never competes with the MX records at acme.com. It serves the custom MAIL FROM subdomain, which lets SPF align and receives bounce feedback. See Publishing your DNS records for what each of the six records does.
Where each record lives
| Name | Record | Serves |
|---|---|---|
acme.com | Your mail provider's MX | Inbound mail to your organization |
<token>._domainkey.mail.acme.com | Mailfully's three DKIM CNAMEs | Signing outgoing mail |
send.mail.acme.com | Mailfully's MX and SPF TXT | The custom MAIL FROM subdomain |
Google Workspace and Microsoft 365
Adding Mailfully's sending records does not touch inbound mail. Leave the MX records Google Workspace or Microsoft 365 hold at your apex as they are.
One SPF record per name
Two SPF records on one name make both invalid. Mailfully's SPF TXT lives on send.mail.acme.com, so it does not touch an SPF record on your apex. If you already publish an SPF TXT on that exact subdomain, merge include:_spf.mailfully.com into the existing record instead of adding a second one.
Verify
Query both names:
dig +short acme.com MX
dig +short send.mail.acme.com MXsend.mail.acme.com should return Mailfully's MX. acme.com returns whatever your mail provider publishes, or nothing if the domain only sends.