Under Change mailbox sync settings, click Options for syncing your content link.To choose when to download an email, select an account.Change the line of text you wish to modify.How to change email signature in Windows 10 Mail appīy editing the Mail app settings, you can change the default ‘ Sent from Mail for Windows 10’ signature and add your own text. It will help you edit the Mail App Signature in Windows 10. If you feel it is very simple in nature and would like to modify it or change it to your liking, read this post. The Mail app in Windows by default adds the ‘ Sent from Mail for Windows 10’ signature to every email you send.