Aliases: extra addresses on a domain

An alias is an address on your domain -- sales@yourdomain.com, say -- that isn't its own mailbox but instead routes to one or more mailboxes you already have. Set one up from Domain > Aliases > New: pick the local part and one or more destination mailboxes on the same domain. Pointing an alias at more than one destination gives you a simple shared inbox, where mail sent to the alias lands in every listed mailbox at once. Aliases can be switched off without deleting them, and can be given an optional expiry for anything meant to be temporary.

Aliases only route to mailboxes on the same domain. If the destination is an address you don't host with Mila, that's forwarding, not an alias -- see Forwarding.

Catch-all: a safety net for the rest of a domain

A domain can have exactly one catch-all: a set of destination mailboxes that receive anything sent to an address on that domain which doesn't match a real mailbox, identity, or alias, instead of the message bouncing. It's useful for tolerating typos in an address, or for capturing mail sent to an address you haven't created yet while you decide what to do with it. Set the destination mailboxes from Domain > Catch-all; clearing all destinations turns it off, and mail to unknown addresses goes back to bouncing normally.

A catch-all left on indefinitely also catches every misdirected and spam-scanning message aimed at your domain, so it's worth turning off once you're not actively relying on it.

How Mila decides where mail goes

For any incoming address, Mila checks it against real mailboxes and their identities first, then aliases, and only falls through to the catch-all -- if one is configured -- as a last resort. An address that already belongs to a mailbox or identity is never redirected by a catch-all.

A note on plus addressing

Mila's mail server treats + as an ordinary character in an address rather than stripping everything after it, the way some providers automatically fold you+tag@yourdomain.com into you@yourdomain.com. If you want that kind of tagging, create an alias for each tag you use, or turn on a catch-all and filter on the full address in your mail client -- either gets you the same result without relying on special handling that isn't built in.