I added a custom sender email but have not received a verification codes

I have followed the instructions above but have not received a verification code

Our apologies. There is indeed no email for that verification through our mail logs. Would you mind trying again to see if it will work this time?

If not, try the SMTP method. 

https://www.jotform.com/help/244-How-to-Setup-SMTP-for-a-Form

The SMTP can also be set up through Account - Settings page:

https://www.jotform.com/help/241-How-to-Edit-Delete-Sender-Emails-on-SMTP-Settings