Service
You can manage protocols used by Synology MailPlus Server to control its communication with other email servers and clients.
Protocol
At the Protocol tab, you can configure the 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.
- Go to Service > Protocol > SMTP.
- Enable the following SMTP-related protocols:
- Enable SMTP: Tick to 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: Tick to encrypt the SMTP connection between your MailPlus Server and other email servers or clients with TLS.
- Enable SMTP-STARTTLS: Tick to encrypt the SMTP connection between your MailPlus Server and other email servers or clients with STARTTLS.
- Save the settings.
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 at Control Panel > Security > Advanced, some email clients (e.g., Outlook 2016) might not be able to establish a connection. To ensure better compatibility, please 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.
- Go to Service > Protocol > Network Interface.
- Select the LAN interface from the drop-down menu.
- Save the settings.
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.
- Go to Service > Protocol > IMAP/POP3.
- Enable the following protocols:
- Enable POP3: Tick to allow POP3 client connections. POP3 allows email clients to download emails from MailPlus Server and save them locally.
- Enable POP3 SSL/TLS: Tick to encrypt POP3 client connections with TLS.
- Enable IMAP: Tick to allow IMAP client connections. IMAP allows email clients to access emails on MailPlus Server and changes made on the client will be synced to the server.
- Enable IMAP SSL/TLS: Tick to encrypt IMAP client connections with TLS.
- Prohibit plaintext authentication over unencrypted connection: Tick to disallow plaintext authentication on an insecure connection. The allowing of plaintext authentication increases the system vulnerability because credentials might be exposed on an insecure connection.
- Advanced: Set the maximum IMAP connection per user of the same IP address at a time. The maximum number is 5,000.
- Save the settings.
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 at Control Panel > Security > Advanced, some email clients (e.g., Outlook 2016) might not be able to establish connections. To ensure better compatibility, please change the TLS/SSL Profile Level to Intermediate compatibility.
Full-Text Search
Allow MailPlus Server to index all users' email content so that you quickly find a specific message with the search function.
- Go to Service > Protocol > Full-Text Search.
- Tick Enable full-text search to index all email content.
- To conduct an accurate search for emails written in Chinese/Japanese/Korean characters, tick Allow character search for Chinese, Japanese, and Korean mail.
- Save the settings.
Note:
- The full-text search function will use more system resources.
MailPlus Client
At the MailPlus Client tab, you can configure various settings applied to all users.
POP3
- Allow users to receive email from external POP3 servers: Tick to 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: Tick to allow client users to freely edit their sender names on a local SMTP server.
OpenPGP
- Disable OpenPGP for all users
Shared Link
- Allow users to create shared links for large attachments: Tick to automatically turn large attachments into shared links to reduce email size.
The following settings should be adjusted as well:
- At 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.
- At Control Panel > User > Advanced > User Home, tick Enable user home service to create a home folder for each user. Large attachments will be uploaded to their individual home folder.
- At Control Panel > 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: Tick to disallow users to add any other shared mailboxes. Mailboxes that have already been shared will not be affected.
Custom Logo
- 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 proportionally compressed.