Simple Mail Transfer Protocol is a part of the application layer. This protocol acts in the store and forward format. The email message you have sent will be first verified by the Sender’s Server. Then, the message will be transmitted to the Receiver’s server. Finally, the message will reach the receiver. To send the message to the right email id, the SMTP protocol will have to close communication with the Mail Transfer Agent (MTA). In some cases, if you receive the error SMTP is not responding and cannot send emails message on your screen, then most probably, it is due to the SMTP server. The SMTP not responding issue occurs due to some mistakes in the email account configuration or while sending email messages. Perform these troubleshooting instructions before trying the advanced methods to fix this issue.