error while trying to send bulk emails using ruby

I'm trying to send some emails using ruby script and i get error after sending to about a few emails then gives the error as shown below. Note: i'm using office365 as smtp provider. this is the initial folder containing the scripts below folder containing the scripts

this is the email handler script below email handler 1

email handler 2

then this is the main sender script main 1

continue main 2

main 3

so when i try to send the mail, first it sends one mail multiple times then the rest email fails as shown below cmd main

then this happens error msg

Now my question is why the emails are failing after sending a very few mails successfully. i think there is an error somewhere in the script. Any help?