Freshsales allows you to choose your own email servers for sending and receiving emails. This functionality lets you make sure that all your email transactions are outside Freshsales, and will be completely managed at your end.
This feature is available from the Blossom plan and can be used with services (like Gmail, Office365, etc.) or private SMTP and IMAP servers. You'll have to ensure the settings are configured properly to ensure that the system is failsafe. You can also opt between enabling your email server for both incoming and outgoing emails, or just for outgoing emails.
To connect your email with IMAP
Go to Profile Settings
and click 
Connect your email. This opens the Connect email section on the profile settings page. Choose an email provider. In this case, click the
Office 365 icon. This brings up the OTHER MAILBOX overlay where you can configure your custom Office 365 sync.
Configuring the email settings:
Fill in your email, username, and password.
Incoming mail settings:
If your email system is Gmail or Office 365, your server name and port details will be pre-filled.
If it's some other system, you need to enter your IMAP server name for incoming emails and you can click on the Use SSL checkbox to establish a secure connection.
Use the drop down to choose the Authentication method.
Outgoing mail settings:
If your email system is Gmail or Office 365, your server name and port details will be pre-filled.
If it's some other system, you need to enter your SMTP server name from where you want the outgoing emails to be sent.
Click on the Use SSL/TLS check box to establish a secure connection.
Use the drop down to choose the Authentication method.
4. Click 
to start using your own email servers.