Receiving emails

[#1]

Recent trouble receiving emails on my IPad.  I receive some emails just as a heading. This is followed by "message not downloaded by Server".  Other emails I receive correctly then when I look at it again later it has gone and the "message not downloaded by Server" appears.  Can anybody help please
JohnL

[#2]

How are you accessing your emails? Using POP3 or IMAP? Can you see the emails when logging into Webmail? It sounds to me like another device is downloading your messages over POP3 before you get the chance to look at them on the iPad.