If you want to change the email account that JotNot sends from, you have two options:  you can change the device-wide default sender email address in Apple's Settings app, or you can change it per email within JotNot.

OPTION 1. CHANGE THE DEVICE-WIDE DEFAULT SENDER EMAIL ADDRESS:

a. Open Apple's Settings app

b. Navigate to Settings > Mail > (COMPOSING) Default Account

c. Change the email account there to the one that you wish to use

If the one you want to use does not show up in the list of options, you'll need to add or re-configure your email account in the Settings app so that it will show up.  Here is Apple's documentation on how to add your email account:

https://support.apple.com/en-us/HT201320

OPTION 2:  CHANGE THE SENDER EMAIL ADDRESS FOR AN INDIVIDUAL EMAIL FROM JOTNOT

a. Open the document you want to send in JotNot

b. Tap on the Share button (box with an up arrow)

c. Tap on "Email"

d. In the email composition window, tap on the line at the top that says "From / CC / BCC".  The line you tapped on should expand into three lines, one for From, one for CC, and one for BCC.

e. Tap again on the "From" line.  A picker wheel should show up at the bottom, showing all of the email accounts that you've configured on your device.

f. Scroll through the picker wheel, and choose the email account that you want to send from.

If the account that you want does not show up in the list of options, you'll need to add or re-configure your email account in Apple's Settings app so that it will show up.  Here is Apple's documentation on how to add your email account:

https://support.apple.com/en-us/HT201320

Please note that the setting in JotNot's settings page called "My Email" is not related to the sender email address that JotNot sends from. Instead, this setting creates a shortcut destination email address, which JotNot will email to, if you choose the "Email Myself" sharing option when sharing a document.