A Gmail poll is usually a Google Form.
Gmail's compose window has no poll. The official workaround is Google Forms. That is a good survey tool. It is a clumsy way to ask one question you want back on the thread.
What Google Forms is
Google Forms collects answers in a spreadsheet. When you send a form you can choose Include form in email. People reading that message in Gmail can often answer without opening a new tab. Other inboxes usually get a link. You can ask many questions, require fields, and accept files. The result lives in the form. A response notification, if you turn one on, is not the same thing as a reply in the conversation.
What Easy Reply is
Easy Reply adds one question and two to four short answers to a Gmail you are writing. The recipient clicks one. They do not install anything. The answer comes back to you on the thread. It is the wrong tool for a ten-question survey, a file upload, or a sheet that someone outside the thread has to sort.
Side by side
Where it starts
Easy Reply. In the Gmail you are already composing.
Google Forms. In Google Forms. You then email the form, or paste the link.
What you can ask
Easy Reply. One question. Two to four answers.
Google Forms. As many questions as you need, including text, files, and required fields.
Where the answer goes
Easy Reply. Back on the email thread, and into Insights.
Google Forms. The form's spreadsheet.
Who can answer in the inbox
Easy Reply. Anyone who can click the button. The click records the answer.
Google Forms. Gmail recipients can often use an embedded form. Other mail apps usually follow a link.
When to use Google Forms
Use Google Forms when you need a real survey, a record outside the inbox, or answers from people who will never see the thread.
When to use Easy Reply
Use Easy Reply when the email is the question. Meeting or not, price or not, still interested or not. One choice, back on the thread.
FAQ
Can a Google Form show up inside the email?
Yes, for many people reading in Gmail, if you check Include form in email when you send it. Other email apps usually get a link to the form. Either way, the answer is stored in the spreadsheet.
Is Easy Reply a poll inside Gmail?
It is answer buttons on the email. You write one question, they click, and the choice comes back on the thread. It is not a multi-question form.
What if I need both?
Ask the one decision in the email with Easy Reply. Send a form only when a yes turns into something you have to collect properly, like a brief or a security questionnaire.
Free for 50 sends a month. The other person does not install anything.