Created the user-guide content (Text and illustrations) (#4683)

* Second attempt

* Small image optimizations

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Co-authored-by: Félix Malfait <felix.malfait@gmail.com>

packages/twenty-website/src/content/user-guide/emails.mdx

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+---
+title: Emails
+info: Understand the concept of email synchronization in Twenty, including how to read synced emails, connect new mailboxes, and set sharing levels.
+icon: IconChecklist
+image: /images/user-guide/emails/emails_header.png
+---
+
+# Email Synchronization
+
+The system links emails from known contacts directly to their CRM records, keeping all communication up to date. It's important to avoid syncing emails from impersonal addresses such as team@ and support@, or from personal email providers like Gmail or Outlook, to ensure privacy and relevance.
+
+## Reading an Email
+
+Go to a specific `Person` or `Company` record page, then select the `Emails` tab to view synced emails instantly. Click on an email to open it.
+
+<img src="/images/user-guide/emails/show-inbox.png" style={{width:'100%'}}/>
+
+You can customize how you share and manage your emails through the settings. 
+
+# Mailbox Settings
+
+## Connecting a New Mailbox
+
+To connect a Gmail mailbox, go to `Settings` > `Accounts`, then click the `Add account` button. You can add several mailboxes to your account.
+
+After connecting a mailbox, visit the `Emails` tab and select the desired mailbox to customize its settings.
+
+The initial import may take some time, and it will be followed by automatic updates every ten minutes.
+
+<img src="/images/user-guide/emails/connect-account.png" style={{width:'100%'}}/>
+
+## Sharing Levels
+
+From here, you can choose different levels of sharing for outbound and inbound emails:
+
+-  **Metadata Only**: Share only the basic information of the email (sender, recipient, date, and time).
+-  **Subject and Metadata**: Share the subject line of the email along with the metadata.
+-  **All Email Content**: Share the entire content of the email, including attachments.
+
+<img src="/images/user-guide/emails/privacy-settings.png" style={{width:'100%'}}/>
+
+## Contacts Auto-Creation
+
+Contact auto-creation is a handy built-in feature. This default feature automatically adds email contacts not already in your CRM, boosting your contact list without any extra effort on your part. To manage this feature, go to `Settings` > `Email`. You can toggle it on or off. Remember, turning it off means that all new email contacts must be manually entered into the CRM.
+
+<img src="/images/user-guide/emails/auto-creation.png" style={{width:'100%'}}/>
+
+## Upcoming Features
+
+Soon, you will have the capability to send emails, view attachments, and request access to email content that you're not allowed to read.