I can't send / check mail through Outlook Express/Eudora/ ?

At first check either you are connected or not (need to take connection). Then check the mailing software configuration by the following procedure.

Configure Outlook Express:

Click Tools ---> Select Account ---> Click Mail tab --->Select the account, which you are using ---> Click properties Button

In the properties window fill up the user information

First in Name text box (user real name)
Fill organization text box (it is optional)
Fill e-mail address (user e-mail address)
Fill Reply Address (same as e-mail address)

Click Servers Tab & Do the Following:

For BOL : Incoming Mail (pop3): mail.bol-online.com
             Outgoing mail (SMTP) : smtp.bol-online.com
For DHAKA.NET : Incoming Mail (pop3): mail.dhaka.net
                             Outgoing mail (SMTP) : smtp.dhaka.net
In incoming mail Server there are Account name and Password option
In account name text box write down your user id
In Password text box write your login password
Click on remember password check box to save the password.
Click on apply and Ok button.

Configure the Eudora Light:

Click Tools --> Click option -->Click Getting Started

In the right side of window POP3 account option pop3 account please write for BOL : user_id@mail.bol-online.com for Dhaka.net :  user_id@mail.dhaka.net. Suppose your BOL user ID is xyz then please write xyz@mail.bol-online.com

Then click return address; write down your e-mail address

Click personal information
Write down your login id
In dialup user name click hosts
Write down smtp.bol-online.com or smtp.dhaka.net in SMTP server

Configure the Eudora 4.0/4.2/5.1

Click tools -->click option-->Click Getting Started

In the right side window click return address write your e-mail address -->Click mail server (incoming) write for BOL: mail.bol-online.com and for Dhaka.net: mail.dhaka.net. ---> Click Login name option - write down user name

In SMTP server type for BOL: smtp.bol-online.com and for Dhaka.net: smtp.dhaka.net.

If you think your all configuration is OK but still not working please fix the DNS numbers in the TCP/IP of the Dialer.