Dedicated sending addresses

Your mail normally leaves from addresses the platform shares between many organizations. The platform's staff can give you dedicated addresses instead (IPv4 or IPv6): only your mail leaves from them, so nobody else's mail affects their reputation. A dedicated address can be your tenant's, your whole organization's, or kept for one of your domains.

Every domain also has an IPv6 address of its own, made for it and used by nobody else, with its reverse DNS set by the platform. Where the platform gives domains their own IPv6 addresses, a dedicated IPv6 address for your whole tenant or organization is not used for them (they would all share it): to give one domain a dedicated IPv6 address, keep it for that domain (Only for).

Seeing and naming them

On the Domains page of the tenant manager (/manage), Dedicated sending addresses lists them (owners, admins, and tenant roles with Domains). For each one:

Only for: one of your domains, or all of them.
Name: its reverse DNS (PTR) and the name it greets other servers with. It must be under one of your proved domains, such as mail.example.com (or the platform's own names). Leave it empty with a domain chosen and it is named mta-….<domain>.
Send from it: turn it off to go back to the shared addresses for a while.

Receivers check that the name points back at the address. Each name under one of your domains shows in that domain's DNS records as an A or AAAA record, with an SPF record of its own (v=spf1 ip4:… -all) for auto-replies and bounces, which receivers check against the name: publish them there (automatic DNS does it for you). The reverse DNS itself is published by the platform where it controls the address's reverse zone; otherwise the page says to ask the provider of the address.

From the command line: corpsuite tenant ips TENANT and corpsuite tenant ip set TENANT ADDRESS hostname=mail.example.com domain=example.com.

What nobody can do

Name an address under a domain that is not yours (another organization's, one you have not proved, or anyone else's): a PTR that claims someone else's name is refused, for staff too.
See or change the platform's shared addresses, or another organization's dedicated ones.
Use a dedicated address for mail from a shared domain (such as mailo.city): that mail leaves from shared addresses, since its people belong to many organizations.

Your domains' SPF records list exactly the addresses their mail may leave from, dedicated ones included.