|Never use a password that you can't remember easily. |
Case is often important - whether the letters are upper case (capital letters) or lower case must be correct. If you have the Caps lock key toggled so it's enabled, an led will light up on your keyboard. Don't have that on unless you had it on when you made the password.
If you go to the web site for the email program, there may be a place where you can click on Forgot your Password ? or similar - if you can supply the correct user name, you can often reset the password to some named default password, then later on make your own unique password.
Or - use the telephone number for the support for the email program.