You probably do not want every email in your Gmail inbox going to Hemma — only the ones from contractors, your architect, and your municipality. Gmail's filter system makes that easy. Set it up once and forget it.
You need:
In Gmail, click the gear icon → See all settings → Forwarding and POP/IMAP tab → Add a forwarding address. Paste your Hemma project email. Gmail will email a confirmation code to that address.
That confirmation email is delivered to Hemma, which means you will see it sitting in your Senders waiting room. Open it, copy the verification code, and paste it back into the Gmail settings page.
You can also click the verification link in the email instead of typing the code, but the code is faster on a phone.
Once you confirm, Gmail itself becomes a sender to your project. Go to Settings → Senders in Hemma and approve it, otherwise future Gmail forwards land in the waiting room.
This is the bit that saves you. Instead of forwarding everything, you create one filter per contractor.
In Gmail, click the search box and then the filter icon on the right. Enter the contractor's email address in the From field and click Create filter. On the next screen, tick Forward it to: and pick your Hemma address from the dropdown. Click Create filter.
Repeat for every contractor, your architect, your municipality, your insurer, your bank — anyone who sends documents related to the build.

For each contractor, search their email address in Gmail, select all messages, and pick Forward as attachment from the more-actions menu. Send them to your Hemma address. Hemma processes the lot.
This is the cheapest way to load months of build history into your project in one go.
Can I just give my contractor my Hemma address and skip filters? Yes — that is even better. Tell new contractors to email the project address directly. Filters are for the people who already have your personal address.
What if I want one contractor's emails to go to both my inbox and Hemma? That is the default. Gmail's "forward" leaves the original in your inbox unless you also tick Delete Gmail's copy on the filter screen. Most people leave both.
What about Gmail labels and starring? Filters can do those too. If you want forwarded contractor emails marked with a Build label, add Apply the label: Build to the same filter.