migrating to Comcast email service. Can we import data via .pst for webmail users?

Migrating email services to Comcast from our current host.  The bulk of my people use outlook so no issue w/ stored emails.  I do have a couple of sales people that do not use outlook and just webmail and have a good number of contacts/emails etc. on our current host.  I can download these into outlook and make a .pst file but is there a way to import this into a our new comcast account so they don't have to start from scratch or have access to historic emails?   

I understand there is a size limitation but I'm sure we are way under that or I'll archive/clean up as needed.