Koma Mail allows you to send and receive mails, encrypted via SSL, through POP3, IMAP (including synchronization), SMTP and WebDav. You can also read your feeds with its integrated RSS viewer.

PopMan will list all e-mails received on your incoming mail server, without having to load these mails with your main email application. Unwanted e-mails can be deleted directly on the server. PopMan will import the settings of your email accounts from your Email application. It can be used to check as many accounts as you want. You can use PopMan to check your e-mail accounts in the background. When new e-mails arrive, you will be notified. To show you whether e-mails contain useful information, or whether they are just spam, PopMan provides a preview functionality. You can use this preview pane to read the text-based content of your e-mails – whether they are plain text or HTML.

Four Outlook Addon Converters convert from EML to MSG, from MSG to EML, and import messages directly into Outlook from EML and MSG formats.

KLS Mail Backup will allow you to back up and restore your Windows Mail, Mozilla Thunderbird, Firefox profile files. The backup files are stored compressed in standard Zip format. You can backup: Windows Mail profile and Windows Contacts; Windows Live Mail profile, Windows Live Contacts and Windows Live Messenger Files; Outlook Express profiles (including mail folders, message rules, internet accounts) and Windows Address Book; Internet Explorer Favorites and Internet Accounts; Mozilla, Seamonkey, Thunderbird and Firefox profiles.

TwInbox is a free Add-in for Microsoft Outlook that will let you use Outlook as a Twitter client.

Mail Attachment Downloader downloads EMail attachments based on personal preferences, without downloading the mail. You can setup various filters to specify what you want to download. You can also setup a schedule for fetching attachments in the background when the program is running. If you often receive pictures or movies from friends as attachments, you could setup Mail Attachment Downloader to automatically download the content to a folder on your hard drive.

TheLetterEncrypter will let you send a secret message to somebody. It features a strong encryption. Entering a password and the message and then pressing the “encrypt” button, is all one needs to do in order to transform a message into jumbled text. This encrypted message can only be unlocked using TheLetterEncrypter and the password that you used when you locked it.

Gmail Alert will notify you for new items on Gmail, Google Apps, Google Calendar, and RSS feeds. It sits on your taskbar until it discovers new messages in up to five separate accounts.

Gmail Notifier will help you check your Gmail accounts.

Outlook Attachment Remover is a free Outlook add-in for saving and extracting attachments, decreasing the size of your Outlook files.

Winmail Opener allows you to view and extract/save the contents of TNEF-encoded messages (winmail. dat). If you receive a winmail. dat file on your e-mail, with Winmail Opener you can view its rich-text contents and attachments. TNEF stands for Transport Neutral Encapsulation Format.

SPAMfighter is a spam and phishing filter for Outlook, Windows Mail and Servers. It harnesses the power of a large community of people who instantly report any spam or phishing messages they receive. Once several people have reported the same email, it is automatically filtered for the rest of the community. In this way, very few people will ever see the spam or phishing email. In addition, a lot of spam and phishing emails are filtered out before they ever reach the community.

Affixa will let you handle “mailto” email links in web pages, send emails directly from almost all the applications on your PC, while automatically attaching files to a new email message, without manually uploading each file to Google or Yahoo; you can also choose to suppress the annoying standard text provided by Windows (“Your attachments are ready to send”).

Spamihilator works between your E-Mail client and the Internet and examines every incoming E-Mail. Useless spam mails (Junk) will be filtered out. This process runs completely in the background. The Bayesian Filter uses the rules of Thomas Bayes (English mathematician, 18th century) and calculates a certain Spam-Probability for every E-Mail. You can train this filter, so the recognition rate will continuously increase. In addition Spamihilator uses a Word-Filter, that searches messages for known keywords. The Spam Word Filter supports Regular Expressions. The DCC-Filter can connect with the DCC Network to recognize unsolicited bulk mail.

* Check also this post on how to easily avoid all of this spam mail you have to check and delete each day!, without using any special program or extension.