setup 5 GB email storage with your domain
MX Records are special entries in the DNS Servers that designate the recipient Email servers for your domain. It is like the zipcode we use in normal postal mails for the letters to be correctly delivered to the destination.
You can access your account in Outlook/ Thunderbird via IMAP for the account to be in sync irrespective of acccessing via webmail or desktop. You can use POP to download the emails to your desktop client, without having the account to remain in sync with the web.
You get 5GB of storage per email with your custom domain. This is based on the size of your messages and attachments.