Warning: Many financial institutions will not allow you to use a forwarded email address for your account. In this case, use your Gmail (or other service) account.
Now that you've gone to the trouble of buying a new domain, we'll call it quackingduck.org, wouldn't it be really cool if you could create custom email addresses for this new domain? How about fred@quackingduck.org or travel@quackingduck.org?
Most domain registrars allow you to create up to 100 unique forwarding addresses. A nice feature is the ability to delete addresses and add new ones if you start getting spam. Many registrars will host your emails for a fee or you can pay a fee to an outside company like Proton Mail. You can also opt to host your own SMTP server, but you had better know what you're doing or your server will become part of a bot farm.
Since I'm not a fan of paying for something I can get for free, I choose to leech off of Google. Use an existing Gmail account or create a new Gmail account, call it anything you want, and you have 15 GBytes of storage for emails, their other services like Google Sheets, or storage for whatever you want. A nifty trick is to create a Gmail account using your domain name like quackingduck.org@gmail.com. Yes, you can use periods in the name, but they are ignored, but it looks nifty to use your domain name. It doesn't matter what you create, something.random@gmail.com would work for the purpose of creating emails for your domain.
Now that you have a new domain and a Gmail account, it's time to set things up.
Step 1.
The two Domain Registrars I use are Namecheap.com and Cloudflare so I'll use those two as examples.
For Namecheap, log in and select "Domain List" then your domain. Go to "Advanced DNS" tab and find "MAIL SETTINGS" and select "Email Forwarding" from the dropdown list. Select the "Domain" tab at the top and find the "Redirect Email" section. Select "ADD FORWARDER" and enter an "Alias" such as "Travel" and the "Forward To" will be your Gmail account. You can also select "ADD CATCH-ALL" and any email name will be forwarded to your Gmail account. This is good for testing. You can turn it off later. Namecheap allows up to 100 unique names.
For Cloudflare, it's a similar process. Browse to dash.cloudflare.com. Select "Account Home" on the left, then your domain name. A new menu will appear. On the left select "Email" then "Email Routing" on the sub-menu. On the right, select the "Routing Rules" tab. In the "Custom addresses" section. select "Create Address". Under "Custom Address", enter e.g. travel@quackingduck.org. Under "Action", select "Send to an Email". Under "Destination", enter your Gmail account. Select the "Active" button to enable it. Repeat the process for as many addresses as you need. In the "Catch-all address" section you can enable this feature for testing.
Step 2.
Gmail configuration is next. I've found that doing this from Chrome browser is easier than using the Gmail app. Make sure Pop-up Blocking is turned off in Chrome settings. Go to Settings > Privacy and Security > Site Settings. Select "Pop-ups and Redirects" and select "Sites can send pop-ups and use redirects". You can turn it back on after configuring email forwarding.
You really, really, really need to use 2 Factor Authentication to log into your Gmail account. Here's the link: Turn on 2-Step Verification. After you set that up, you will need an app password to bypass 2 Factor Authentication just for the purpose of sending and replying to email names created for your new domain. Use the app password only for this purpose and save it some place secure. A Post-It note stuck to your monitor is not secure.
To create an app password for Gmail go here: Sign in with app passwords.
Log in to your Gmail account, select "Settings" then "See all settings". Under the "Accounts and Import" tab, select "Import from another address" in the "Import mail and contacts:" section. I don't remember all the steps involved. Just follow the prompts.
At this point, you should be able to send emails to your newly created addresses. You may have to create a filter to apply a label to any email sent to the domain name.
To reply to these domain emails or "Send As" using this address, you will need to add each domain email name in the "Send mail as:" section. Select "Add another email address". You will get a pop-up for the next steps (I warned you!). Enter your name (can be anything) in the "Name:" section. In the "Email address:" field, enter the custom email address e.g. travel@quackingduck.org. Leave "Treat as an alias" turned on. Select "Next Step". The SMTP Server name should be smtp.gmail.com Port 587. The Username is your Gmail address and the Password will be the Application Password for the Gmail account. Select "Add Account". Do this for every email address you create.