Insufficient system storage

Hello,
While using SMTP application, sometime my process is working properly but sometimes I’m getting one error.
Error :
Insufficient system storage. The server response was: Error writing message to safe storage; insufficient temp disk space for import.

Please help me with this issue, so that I can work properly on the process.

Thanks

You can check SMTP Server - Error “insufficient System storage” indicates the receipt mail server is low on disk space or free memory and it cannot receive new messages.