Should I use a shared inbox or forwarding?

The distinction matters more than it appears. An address that forwards is a redirect: the mail arrives in somebody's personal mailbox, replies come from their personal address, and the entire correspondence history lives in an account the business does not control. When that person leaves, or their account is closed, the record of every customer conversation goes with it.

A shared inbox is a mailbox in its own right that several people can open. Replies come from the business address rather than from an individual, the history stays in one place, and access is granted and revoked without touching anybody's personal mail. That last point is the practical difference: removing somebody from a shared inbox is a setting, while removing somebody from a forwarding arrangement means changing a password everybody was using.

For a genuine business of one, forwarding is adequate and there is a specific condition attached. The address must exist as a real mailbox on your domain rather than as an alias pointing at a personal account, because a mailbox can be logged into, backed up, and handed over while an alias cannot. Many hosts offer both and the difference is easy to miss at setup.

Move before the first hire rather than at it. Migrating a mailbox with two years of history while somebody is starting is considerably harder than doing it in advance, and the moment you actually need shared access is the moment you have the least time to arrange it.

Whichever you use, reply from the business address rather than from your own. Customers who receive a reply from a personal address will use that address next time, which quietly recreates the problem you were solving and means the history is split across two places.

Set up the function addresses you will actually use and no more. Something for enquiries and something for billing covers most first year businesses, and each additional address is another place to check. An address nobody monitors is worse than not having it, because customers use it and receive silence.

Decide what happens when somebody is away before it arises. A shared inbox handles this automatically since somebody else can open it. A forwarding arrangement requires either an out of office or a change to the forwarding, and doing that while somebody is unreachable is the situation to avoid.

Then check that both arrangements are actually delivering. Forwarding chains break silently, particularly where the destination is a consumer mail provider that decides forwarded mail looks suspicious, and the failure is invisible because nobody receives a bounce. Sending yourself a test message from an outside address once a quarter is the whole check, and it catches the one failure in this area that costs you customers without any indication that it is happening.

Consider what happens to the mailbox if you stop trading or sell the business, since the address is part of what a buyer would be acquiring and a mailbox on your own domain transfers while a forwarding arrangement into a personal account does not. This is a small consideration now and it is one of several reasons the mailbox should belong to the business from the beginning.

Set up an out of office on the mailbox itself rather than on a personal account, so it applies regardless of who is monitoring it and does not disappear when somebody changes their own settings.