In 2011 I used Gmail as a central place for email from several internet projects. I forwarded messages from different domains into one inbox and could reply from the address the customer had written to. That saved switching between separate mailboxes.
The old setup can no longer be recommended without qualification. Google has announced that from January 2027 Gmail will stop sending as outside, non-Google addresses. Gmailify and web-based POP fetching of outside mail will also end. New configurations may be restricted sooner. Google says automatic forwarding from another provider to Gmail will remain possible, but that does not restore the outgoing address feature.
Receiving and sending are separate choices
You can forward messages to one inbox for reading. Check where the original is stored, whether spam filters may catch important mail and whether replies leave from the right business address. Test with a second address of your own before changing how customers contact you.
For several outside accounts, Google lists the provider's own website, a desktop app using IMAP/SMTP and the Gmail mobile app among the alternatives. Google Workspace addresses and Google-hosted aliases retain other options. The right solution depends on your domains, devices, security needs and whether you truly need everything in one web inbox.
Make the transition manageable
List every address first. Record where new mail arrives, which address you reply from and who needs access. Then check current settings with both providers. Do not rely on my screenshots or menu paths from 2011: they belong to a different period of Gmail.
The lasting lesson is that central handling can save time. You now need to choose the technical route again because receiving and sending in Gmail no longer offer the same possibilities.