Knowledge Center

Service

You can manage protocols used by Synology MailPlus Server to control its communication with other email servers and clients.

Protocol

On the Protocol tab, you can configure SMTP settings, network interface, IMAP/POP3 settings, and full-text search.

SMTP

Enable SMTP to let your MailPlus Server communicate with other email servers and clients.

  1. Go to Service > Protocol > SMTP.
  2. Enable the following SMTP-related protocols:
    • Enable SMTP: Allow MailPlus Server to communicate with other email servers/clients via SMTP.
      • Account type: Select the user type (i.e., local users, LDAP users, or domain users) that is allowed to use email services.
      • Port: Assign a port for the SMTP connection. The default port is 25.
    • Enable SMTP-SSL/TLS: Encrypt the SMTP connection between your MailPlus Server and other email servers or clients with TLS.
    • Enable SMTP-STARTTLS: Encrypt the SMTP connection between your MailPlus Server and other email servers or clients with STARTTLS.

Note:

  • When you switch the account type, an alert window will appear. Different account types have different email addresses, so emails under different account types cannot be shared but will be migrated. If you want to migrate emails from Local Users to LDAP Users or Domain Users, then click Yes in the alert window.
    The system will only migrate emails to the directory service accounts with the same usernames as the local users. Accounts with different usernames will be ignored.
  • If you have enabled SMTP-STARTTLS in MailPlus Server and set the TLS/SSL Profile Level to Modern compatibility in Control Panel > Security > Advanced, some email clients (e.g., Outlook 2016) might not be able to establish a connection. To ensure better compatibility, change the TLS/SSL Profile Level to Intermediate compatibility.

Network Interface

Bind to a network interface for the server communication under the MailPlus high-availability structure.

  1. Go to Service > Protocol > Network Interface.
  2. Select the LAN interface from the drop-down menu.

IMAP/POP3

Enable IMAP and POP3 to allow third-party email clients (e.g., Apple Mail and Microsoft Outlook) to access emails on MailPlus Server.

  1. Go to Service > Protocol > IMAP/POP3.
  2. Enable the following protocols:
    • Enable POP3: Allow POP3 client connections. Email clients can download emails from MailPlus Server via POP3 and save them locally.
    • Enable POP3 SSL/TLS: Encrypt POP3 client connections with TLS.
    • Enable IMAP: Allow IMAP client connections. Email clients can access emails on MailPlus Server via IMAP and changes made on the client will be synced to the server.
    • Enable IMAP SSL/TLS: Encrypt IMAP client connections with TLS.
    • Prohibit plaintext authentication over unencrypted connection: Disallow plaintext authentication on an insecure connection. Allowing plaintext authentication can increase system vulnerability, as credentials may be exposed on an insecure connection.
    • Advanced: Set the maximum number of simultaneous connections allowed for a user to access their email account via POP3 or IMAP protocols from the same IP address. The maximum value is 5,000.

Note:

  • If you have enabled POP3 SSL/TLS or IMAP SSL/TLS in MailPlus Server and set the TLS/SSL Profile Level to Modern compatibility in Control Panel > Security > Advanced, some email clients (e.g., Outlook 2016) might not be able to establish connections. To ensure better compatibility, change the TLS/SSL Profile Level to Intermediate compatibility.

Full-Text Search

Enable MailPlus Server to index email content for efficient message searching.

  1. Go to Service > Protocol > Full-Text Search.
  2. Select Enable full-text search to index all email content. Keep in mind that enabling this feature will require additional system resources due to the indexing process.
  3. To conduct an accurate search for emails written in Chinese/Japanese/Korean characters, select Allow character search for Chinese, Japanese, and Korean mail.

MailPlus Client

On the MailPlus Client tab, you can configure various settings applied to all users.

POP3

  • Allow users to receive email from external POP3 servers: Allow users to fetch external emails to MailPlus via POP3. You can specify the receiving interval in minutes.

SMTP

  • Allow users to change the sender name on the local SMTP server: Allow client users to freely edit their sender names on a local SMTP server.

Mail Encryption

  • Allow users to encrypt emails with OpenPGP
  • Allow users to encrypt emails with S/MIME

Shared Link

  • Allow users to create shared links for large attachments: Automatically turn large attachments into shared links to reduce email size.
    The following settings should be adjusted as well:
    • In MailPlus Server > Domain, double-click the domain and go to Usage Limit to specify the attachment size limit. Files exceeding the set limit will be converted to shared links.
    • In Control Panel > User & Group > Advanced > User Home, select Enable user home service to create a home folder for each user. Large attachments will be uploaded to their home folder.
    • In Control Panel > Application Privileges, allow all users to use File Station so that they can create or delete shared links on their own.

Shared Mailbox

  • Disable the sharing feature to prevent users from sharing mailboxes: Disallow users to add any other shared mailboxes. Existing shared mailboxes will not be affected.

Custom Logo

  • Upload an image here to change the logo in the upper-left corner of the MailPlus window.
    • Maximum image file size: 1 MB
    • Logo dimensions: The suggested logo size is 128 x 40 pixels. If the uploaded image exceeds the size, it will be compressed proportionally.
Protocol
SMTP
Network Interface
IMAP/POP3
Full-Text Search
MailPlus Client
POP3
SMTP
Mail Encryption
Shared Link
Shared Mailbox
Custom Logo