Sounds like a great question for their facebook page:
https://www.facebook.com/mymail.official
Their website ( my.com ) doesn't seem to have a support section for their free apps.
Link doesn't work.
Smartphone, Samsung Galaxy S5, Lollipop 5.0, Verizon network
Are there any users of myMail on a smartphone able to add FOLDERS. The apps support team, after about two weeks of communication, is unable to solve the problem. The error message I receive when I try to set up a new folder is
"unable to create folder. Please try later."
Are there any other users that have been successful? Thanks.
Smartphone, Samsung Galaxy S5, Lollipop 5.0, Verizon network
If the MyMail app support team cannot help, then it is likely to be not possible. Try another email app, such as Email TypeApp Mail - Free from the Play Store, which has the ability to create and organise folders under, "Folder Management".