I cannot send emails to a group of contacts it says the mail boxes are full

I am unable to send emails to groups of contacts. I keep receiving this error code:

File: outlook\pstprx\storeas\utils\airsyncstatuscodes.h

Line: 104

HTTP/1.1 200 OK

MailStatus: 115

To re-try press F9...

Error Code: 0x80004005

It says that my mail boxes are full.

Please help. This is extremely frustrating and is costing my business.

These are mail recipients who have requested that I send them emails (my customers) and I am unable to contact them.

Thanks.

Jackie

Question about Outlook Express