email not always polling (using talktalk)

hi i use talktalk email, on the sgs it is reallt unreliable and doesn't always check for new mail, i do have the settings to check every 15 minutes, also the messages take a VERY long time to delete and often crashes, i  now use k9 email but that doesn't always check either

could it be a phone problem or talktalk??

model number: GT-I9000
Firmware: 2.2
Baseband: I9000XXJPP
Kernal v:  2.6.32.9 root@sep-35#1
Build:      FROYO.XXJPO