ESB suspends during processing big message

Hi gurus,

i have the folllowing scenario in PI 7.31 Java-Only.

Proxy --> PI --> SFTP File

When small test message is sent, it works well.

Today Proxy sent a big message (1,058 KB) and got the following error:

javax.resource.ResourceException: 4: Putting /download/20140702-075502-1414 failed.

I download the payload and tested it in the ESB. ESB suspends without any reaction.

Could you tell me what for a problem here?

Thanks and regards

Christine