PopTrayU if a free Email notifier for Windows, it is a derivative work of PopTray.

1. Preview
When you click the preview button (or double-click a message) PopTrayU will show the Preview window and then start retrieving the message from your E-mail server. If your connection is slow, or the message is huge, this can take quite a while.

2. Accounts
Clicking on the accounts tab on the right-hand side allows you to define all your e-mail accounts.

3. Rules
Rules allow you to perform various automated tasks as new e-mails arrive depending on the contents of each message.

4. Tray
PopTrayU will display an indicator in your system tray at all times.

Interval Options:
How Often Should PopTrayU check for New Mail?
* Interval (Check for mail every...minutes)
* Don't automatically check for new messages
* Set Interval per Account
Interval Check Conditions
* Only Check When Already Online
* AutoCheck only when Minimized
* Don't Check Between

Defaults Options:
* E-Mail Program
* Default Sound
* Language
* User Data Folder

General Options:
Startup
* Check for New Mail on Startup
* Start Minimized
Tray Icon
* Rotate Icon for each Account
* Reset Mail Count in Tray when Viewing
* Tray Icon While Checking
New Message Notification
* Flash Tray Icon
* Show Balloon Notification
* Use Deluxe Balloon
* Show Main Window

Advanced Options:
Advanced POP Settings
* Connection TimeOut
* Enable Quick Checking
* Safe Delete (using UIDL)
Error Handling
* Ignore Connection Errors
* Ignore Retrieve Errors
* Show Errors in Balloon Popups
Message Download
* Preview Top Lins
* Retrieve Body while Checking

Advanced Options - Main Window:
Main Window Message List
* Indicate Viewed and Unviewed Message
* Remember Viewed Messages
* Hide Viewed Messages
* Show Messages while Checking

Main Window Behaviors
* Stay on Top
* X Button Minimizes
* Minimize to Tray
* Multi-line Account Tabs
* Double Click Delay on Click
* Password Protect
* Default Spam Toolbar Button Action

Advanced Options - Miscellaneous:
Message Deletion
* Deletion Confirmation
* Extra Confirmation when Deleting Protected Messages
* Delete Mail only on Next Check
Mail Client Communication
* MAPI instead of mailto:
Rules/Blacklist
* Log Rules
* Black List mark as Spam
Message Preview Options
* Disable HTML Preview

Command-line Options:
Usage:
PopTrayU [Path to INI file] [/MULTIPLE] [/ACTION:actionname] [/QUIT]
Options:
1. MULTIPLE
Allow multiple intances of PopTrayU. With this switch and new copy of PopTrayU will be launched. Otherwise the existing running copy of PopTrayU will be given focus.
2. ACTION
Execute one of the Mouse Actions. The following actions are supported: Show, Check, RunClient, CheckShow, Info, CheckInfo, Window, AutoCheck, New, Sound, DelSpam, MarkViewed, AutoCheckOn, AutoCheckOff, SoundOn, SoundOff.
3. QUIT
Closes the running copy of PopTrayU and then exit.

The license of this software is Free, you can free download and free use this email checker software.