Outgoing mail server configuration (SMTP) is required if you want to send Confluence pages via email. It depends on which email provider you are using, but the easiest way is to ask your system administrator, he will know for sure.
Before you save it, please test if your connection is valid.
Password Encryption
Galois/Counter Mode (GCM) is a recommended algorithm for authenticated encryption with associated data. GCM is constructed from an approved symmetric key block cipher with a block size of 128 bits, such as the Advanced Encryption Standard (AES) algorithm. Thus, GCM is a mode of operation of the AES algorithm.
Don’t worry, you password is safe 
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SMPT server details have some required and optional fields:
Server Name - It is required for and used to identify the email server in Confluence.
From address - It should have the same domain as the configured SMTP server. (no-reply@caelor.com)
From Name - Will display in notification emails.
Subject Prefix - Will append to the subject line of notification emails
