Synology MailPlus Technical Specifications

Application component

Synology MailPlus Server

Features

Privately-owned mail service on a Synology NAS, providing multiple domain centralization management, user policy, and mail logs for easy management
Cross-platform mail solution for accessing emails on computers or mobile devices
Full-fledged security features for the defense against malicious attacks: Rspamd anti-spam mechanism, spam auto-learning, ClamAV anti-malware, and advanced SMTP security
High-availability cluster for an uptime mail service during system updates and hardware replacements via switching the mail system to the paired server in seconds
Seamless mail migration tool designed for Gmail, Google Workspace, Microsoft Exchange, Yahoo, and other IMAP servers

Specifications

Monitoring
- Outgoing emails sent, resent, or unable to be sent from your Synology MailPlus Server, and incoming emails received or rejected by your Synology MailPlus Server
- Real-time server information including high-availability cluster status
- Statistics of various kinds of email threats presented by graphs
- Statistics of blocked inbound and outbound emails respectively, along with top senders/recipients of such emails
Management
- Multiple domain management and configuration settings related to alias, auto BCC, usage limit, and disclaimer in Synology MailPlus Server
- SMTP authentication that forces clients to provide user credentials for login while connecting to Synology MailPlus Server via SMTP
- SMTP settings and diverse policies for blocking emails that exceed the limits: hostname, SMTP banner, the maximum number of recipients per email, the maximum number of email hops, and the maximum size per email for Synology MailPlus Server
- External postmaster, which is set to receive system emails sent to Mailer-daemon and postmaster aliases from other mail servers
- Mail delivery settings that allow sending emails through other mail servers so that mail content will not be exposed to the Internet and subject to possible attacks
- Synology MailPlus as a relay server that sends emails for servers listed on the trusted list, and receives emails listed on the domain list
- Block and allow lists to reject, discard, or accept emails that match the set criteria
- Connection policies for blocking emails from unidentifiable domains and hosts that cannot be identified or may cause Synology MailPlus Server to be overloaded
- Smooth communication between Synology MailPlus Server and external mail servers/third-party clients via SMTP, POP3, and IMAP
- The high-availability structure which maximizes the service uptime during system updates and hardware replacements by switching the mail system to the paired server in seconds
- Mailbox quota and the corresponding notification settings for the control of data growth
- Mailbox details including sizes and user statuses displayed on the console for easy management
- Batch deletion of deactivated users' mailboxes to quickly free up storage space
- Mail import and export:
  - Emails can be imported to a user's mailbox in the SMC or PST format
  - Users' mailboxes can be exported to SMC files
Security
- Custom spam filtering rules work with auto-learning to achieve accurate detection
- DNSBL filters out spam published through the DNS based on a list of IP addresses of computers or networks
- Greylist returns a temporary error to mail clients
- Antivirus engines ClamAV and McAfee (paid option) scan all incoming and outgoing emails for viruses. When an email is found infected, the system will delete or quarantine the email and send notifications to the intended recipients
- ClamAV antivirus engine databases, such as Google SafeBrowsing database or a third-party database, help detect malicious links in emails
- Virus definitions are automatically updated according to the custom schedule
- Various authentication mechanisms, including SPF, DKIM, DMARC, and DANE, guard against spam and identity theft
- Emails with potentially dangerous elements will be filtered out when scanned by content and attachment file types
- MCP (Message Content Protection) rules can filter or block targeted emails. If an email is matched with the rule's criteria, the rule score will be the total sum of the MCP score. If the total MCP score exceeds the MCP threshold score you defined, the mail system will execute the action you have selected from the following: Save to quarantine, Deliver anyway, Delete mail, Notify sender, or Forward
Auditing
- Displays logs of the mail queue for users to view the status of emails and to control emails in the queue
- Displays logs regarding incoming/outgoing emails from your Synology NAS
- Displays administration logs to record setting changes made by administrators
- Allows keyword search for deleting or exporting emails
- Forwards logs to another server to back them up or transfers logs to a syslog server for centralized management
- Tracks the mail system/traffic and sends logs periodically
Mail Migration
- Seamless migration tools for Gmail, Google Workspace, Microsoft Exchange, Yahoo, and other IMAP servers
  - Supports reusing system configurations from Microsoft Exchange for a quick system replacement
  - Supports migrating emails from Google Workspace (Gmail) per label, with the original structure remaining intact
- Multiple tasks for mail migration from external mail servers: custom filters for bypassing spam emails, emails received after a specific date, and emails exceeding the size limit (KB)
- Mail migration without asking for access permissions of each source Exchange user account as long as a delegated account is available
Sizing
- Maximum number of concurrent users: 4,000
- Maximum number of emails processed per day: 5,721,000

Limitations

The user limit and the number of emails that can be processed per day vary for different Synology NAS models. For details, refer to the product specifications or the Synology MailPlus license page
To ensure the smooth running of security engines, it is recommended that you use models with at least 2 GB RAM

Synology MailPlus

Features

An intuitive and powerful webmail client designed for organizing emails and sharing mailboxes with work partners
User interface like three-column mode and the option for conversation view to better fit user experience
Custom filters and priority mailbox for effective mail management
Shared mailboxes to centralize emails of a specific project
A hub of communication and schedules through its seamless integration with Synology Chat and Synology Calendar

Specifications

Compose
- Auto-complete list based on recipient email addresses saved in Synology Contacts
- Auto-saved drafts
- S/MIME and OpenPGP for email encryption and signing
- Send cancellation period of 5, 10, 15, 20, or 30 seconds
- User-defined text styles: font styles, font sizes, and colors
- Auto-reply/forward based on user settings
- Schedule send to deliver emails at a specific date and time
- Mail merge for personalized mass mail (Learn more)
- Mail templates to save frequently used text and images for reuse
Mail Management
- Centralizes management with a priority mailbox collecting emails from various mailboxes or labels
- Supports nested labels for hierarchical classification
- Filters emails with custom exception rules for email organization
- Allows sorting emails by starring, archiving, moving to customized mailboxes, as well as adding labels
- Allows sharing mailboxes with internal users/groups to centralize emails over a specific project. Specific access permission to a shared mailbox can be assigned to each user/group
- Allows archiving a mailbox to make all the archived emails appear in this mailbox
- Provides two columns and three columns for the split pane mode, with additional layout options for two columns: one line without preview, one line with preview, and two lines
- Provides a universal search bar with syntax operators to quickly find a specific email
- Has flexible options for the display of external images: always display external images or ask before displaying. The latter prevents malicious senders from exploiting externally linked images
- Sends push notifications with a browser extension (optional)
- Displays emails in the conversation mode or the individual message mode. In the conversation mode, a single email will be grouped with all its replies
- Displays mailbox usage and sends warning messages when approaching the storage limit
- Supports previewing various file formats of email attachments using Universal Viewer
General Settings
- Supports multiple signatures for different scenarios
- Restores a conversation wrongly identified as spam
- Allows adding additional SMTP servers or editing existing ones according to personal preference. For example, you can add the Google SMTP server and enter your Google account and password to send emails via your Google account in Synology MailPlus
- Custom POP3 servers and predefined ones (e.g., Gmail) for fetching emails from different servers to Synology MailPlus
Administrator
- Allows users to receive emails from external POP3 servers
- Allows users to share links for large attachments
- Allows users to use S/MIME or OpenPGP to encrypt and sign emails
- Allows users to customize the logo in the Synology MailPlus web portal
Integration
- Integrates with Synology Chat and Synology Calendar, serving as a hub of communication and schedules. With the plug-ins of Synology Chat and Synology Calendar, users can dive into project discussions and add emails to your to-do list right from Synology MailPlus
- Adds a conversation to Synology Calendar tasks

Affiliated Utility

Synology MailPlus (Mobile)

Features

Intuitive user interface for composing mails, receiving mails, and managing mails across Android or iOS devices
Labels and user-defined mailboxes for custom mail organization
Multiple templates, various built-in stickers and emoji for a quick reply

Specifications

System requirements
- iOS: 16.0 or above
- Android: 9 or above

Email management
- Conversation view for intuitive mail browsing
- Easy ways to keep mailboxes organized: apply labels, move to a certain mailbox, and mark as starred/read/unread
- Localized email address to send emails with or receive emails from email addresses in native languages (e.g., Chinese and Russian)
- Swipe gestures for moving across the next or previous email thread
- Actions on email notifications: delete, archive, and mark as read
- Undo operations for the labeled actions: delete, move, archive, and remove
- Mail printing in a thread
- Image viewer for viewing attached images without downloading
- Manual events adding to Synology Calendar
Security
- Passcode lock for data protection (Touch ID supported)
- OpenPGP for email encryption and decryption
- Reports of suspicious emails sent to the system administrator for spam learning enhancement
Settings
- Account switching to receive notifications from different sources without repeating the login process
- Custom swipe options: delete, archive, mark as Spam/Not Spam, mark as read/unread, apply labels, move to a certain mailbox
- Custom preview lines based on user preferences
- Font size settings: large, medium, small
- Push notifications when there is an email received in the user-defined mailboxes
- Mobile signature settings for sender information display
- Multiple templates for a quick reply
- Auto remote images loading
- Email content prefetching on Wi-Fi only
- Integration with Synology Calendar or other calendar applications
- Mailbox management: create, edit, and delete mailbox
- Label management: create, edit, and delete labels
- Cache storage limit for images and attachments
- Dark theme settings