Duplicate emails sent to your contacts or inbox

Here are some of the most common reasons duplicate emails can be sent from Salesforce.

Reasons duplicate email are sent to your contacts or inbox
 

1. Duplicate emails may be sent because of a mechanism that Salesforce has built in to ensure that each email reaches its intended recipient.

• To ensure delivery, each email contains data to signify the end of the email. When mail servers receive this data, the email is considered to have reached its intended recipient. When the 'end of message' data is not processed by the recipient's mail server, generally due to a miscommunication between the mail servers, the Salesforce mail server assumes that the email was not properly received, and resends the email.

2. On some objects when you double or triple click the send button on an email from Salesforce can cause multiple emails to go out to your contacts. This only happens in the classic UI, as the Send Email button is disabled in the Lightning Experience after it is clicked. 

To know which of the 2 scenarios applies to you 
 

• When the email timestamps are 2 minutes apart, then it is due to reason #1.
• When the email timestamps are the same, then it is due to reason #2.