The invoice I generated is not getting emailed to the customer. What settings do I need to check?

To resolve the issue of the invoice not getting emailed to customer 
you need to follow the steps 
Step1 To configure the gmail with BUSY go to administration menu
Step2 Click on Configuration and then click on Email Configuration
Step3 on email setting option Make it Send Directly
Step4 on send reports as option select pdf attachment or email body text or 
or XML attachment or PDF and xml attachment 
Step5 on server configuration option select smtp server and type smtp.gmail.com
Step6 On username option type your gmail ID
Step7 To create the password open your gmail and go to Click on the top right side google apps option and click on account
Step8 after opening google account option click on security 
then click on 2 step verification option put your gmail password and click 
on next and enable 2 step verification
Step9 after enabling two step verification go to search google account option 
and type app password
Step10 select the app password option and type app name as BUSY then click on create 
Step11 select the app password option and type app name as BUSY then click 
Step12 after clicking create option a pasword will appear on screen 
Step13 Copy the password and paste it on BUSY mail password under server 
configuration option
Step14 after these steps click on From option on the the right side of email setting and type the name which you want to show the party in mail
Step15 Click on reply to option and select mail id in which you want a reply of mail send 
step16 Click on email header and footer option and type the header footer if any you wanted to show in mail 
Step17 after all the steps click on save 
Step18 ensure customer mail id given properly while send mail 
create