attachments renamed to ATT0000*.dat

I have a mail server installed on FreeBSD 4.9 that has been running fine
for months.
About 5-6 days ago people started saying that there attachments are not
showing up, this is what happens.
If I were to send a PDF attachment named test.pdf to my ISP e-mail
account via sqwebmail it would show up as ATT000014.dat.
I can resave this file with the PDF extension and open it just fine.
This only seems to happen when using sqwebmail, if we send via outlook
everything is normal.
Has anybody else seen this before?