Unable to send automated mail using udev and msmtp

Question

I am trying to write a script to send an email whenever a usb device is connected to my computer (Arch Linux). The code I wrote is

#!/bin/bash
if [[ ! -z "$1" ]]; then
    echo "USB inserted at $(date) for $1 and $2" >> /home/user/commands/logs.log
    cd ~
    ip -4 addr | grep -oP '(?<=inet\s)\d+(\.\d+){3}' > /home/user/commands/testing.txt
    echo -e "Subject: Hello \n\nBody:usb inserted at $(ip -4 addr | grep -oP '(?<=inet\s)\d+(\.\d+){3}')\nthrough the mail" | msmtp [email protected]
fi

the script is supposed to send the ipv4 address to the mail. The usb insertion is being detected and the log file and testing txt file is being written.

But the mail is not being sent. I wrote the mail code separately through the terminal and it seems to be working. But inside the code, the mail is not getting run.

I have set the msmtp working. I have checked using terminal commands directly and it is working. But through the script it is not working.

All other commands are getting executed and I am getting the files.

This is my rules script

ACTION=="add",\
SUBSYSTEMS=="usb",\
ENV{DEVTYPE}=="usb_device",\
RUN+="/usr/local/bin/usbinserted.sh '%E{DEVTYPE}' '%E{DEVNAME}'"