Poor mail retrieval success on Mac Mail 8.1 (POP)

I recently set up Mac Mail 8.1 as my POP email client. My email service is through a webmail account I have with netfirms.com.

When I click "Get new mail" the activity window says that it is fetching new mail, however it often gets stuck on "preparing to retrieve messages..." with none making it to my Mac Mail inbox.

Occasionally some emails come in, however it is very slow in doing so; 10 - 15minutes after clicking "Get new mail". additionally, the message retrieval activity concludes after a small fraction of what is in my webmail inbox comes into the Mac Mail inbox; it never finishes the job of fetching mail.

When I click on "Get new mail" again it is hit and miss (more often a miss) as to whether it will bring in new messages or get stuck on "preparing to retrieve messages..."

When I go to the connection doctor my POP account is connected to the server, and I do not get any error messages, so I am at a loss to explain what is happening. It sometimes works, mostly not, and when it does it is very slow in doing so and has only brought in a very small number of the emails it should.

Any ideas?