Historically, Zoho CRM only let you send emails from a Contact-based record, such as a Lead or Contact. If you needed to email someone while working at Account level, you had no direct way to do it without switching to the linked Contact record first. Zoho CRM now supports sending emails directly from the Account record itself.
Accounts often represent a business relationship with several Contacts attached, and sometimes the email you need to send relates to the Account as a whole rather than a single individual. Being able to send from the Account record directly avoids unnecessary navigation and keeps the email logged where it's actually relevant.
Emails are available as a related list on Leads, Contacts, Deals, Accounts, Quotes, Invoices, Sales Orders, Purchase Orders, Cases, Vendors, and custom modules. Your default From address is the one you signed up with, or your integrated mailbox if you've connected one via IMAP, POP, or the Gmail API, and you can add further sending addresses under Setup, then Email, then Email Configuration, then More From Addresses.