MailCal has a multi-select mode that allows you to select multiple emails at once and take action on them. There are two ways to trigger the multi-select model: 

  • When viewing emails in a folder, long press ANY email, and it will put you in multi-select mode. 
  • Alternatively, when viewing emails in a folder, open the overflow menu (... at the top), and use the option labeled as: "Multi Select Items"

Once you select multiple items, you can once again use the overflow menu to take actions on selected emails.