I wish to download all emails and put it within a .txt file. Then I want to send selected emails to selected people using any keywords in the email

[Taifun]

Make yourself familiar with parsing something

App Inventor Code Snippets | Pura Vida Apps

And for more advanced requirements, learn regex... try a Google search... there are regex extensions available... you can find them in the extensions directory App Inventor Extensions | Pura Vida Apps

However my actual advice for you is: rethink your design... what I can see up to now is, that there are several half automatic cumbersome steps involved in your e-commerce project... sending csv files... parsing emails... see again my advice here

Give some tips to create an app that has options to get ecommerce selling data like 1) Product Name, 2) Product image, 3) Price etc

Your description is already too much technical... Isn't it like this: you want to collect product data (name, description, price, image, etc) from users and then sell these products for them? Like Amazon? Usually you would use an online database to store the data. This could be any online database, for example MySQL. The images could be stored on a web server and the links to the images in the database. Like this, there is no conversion to base64 and later no conversion from base64 to get t…

Also it looks like you do not know how to work independently... every 5 minutes you have another question... use the search feature of the community more frequently and first learn some basics... see also

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Taifun