Why are messages marked as read when checking my Exchange Server email?
Your Exchange Server may have settings which by default mark emails retrieved from your device as read. Please contact your system administrator to find out what settings your Exchange Server uses.
Why can't I set up my email account?
Double-check information your email service requires to set up your email account. You will need to know the correct SMTP/POP3/IMAP/Exchange settings, and may also need to find out the security type, ports, and if any domain names are needed as part of the username.
Why can't I view some attachments?
Some attachments may not be supported by the device. You may browse the Market to find programs that may support the file type you would like to view.
How do I send a text message?
From the Messaging application tap Compose message. Enter the mobile phone number or name of the message recipient in the To field. As you enter this information, matching contacts will appear on the screen. Select the desired contact. Type the message below and tap Send.
What types of email does my device support?
Microsoft Exchange, Gmail™, IMAP4 and POP3.
How many email accounts can my device support?
Ten accounts. One Exchange account and the rest as Gmail, IMAP, or POP accounts.
How do I edit my signature on my email account?
To change your signature on the default email application in HTC Sense™, press All programs on the Home screen > Mail > Menu > More > Settings > General settings > Signature to edit your own signature.
To change your signature in your Gmail account please press All programs on the Home screen > Gmail > Menu > Settings > Signature to edit your own signature.
NOTE: The email program on your phone is different from the Gmail application and thus has different settings. To use the signature feature, you must first set up the appropriate email account on your phone.
How do I send a meeting request from my phone?
To send a meeting request, from the Exchange ActiveSync account tap Menu > More > New meeting invitation. Enter the meeting details and then tap Send.
How do I set or remove an Out of the Office message?
To set the Out of the Office message, from the Exchange Activesync account tap Menu > More > Out of the Office. Modify the settings as desired and then tap Save.
Original Source: http://www.htc.com/us/support/evo-sprint/help/messaging