Hi Welcome to JustAnswer.com I am Tech Specialist and today, I will be trying my best to solve your issue.
Are you trying to increase your road runner mailbox size?
Your response came in at 1am, therefore, I was not able to respond to you quickly. If using mail client won't be a very effective access from my phone, how can I solve my 705% too full mailbox, without increasing my internet service fee?Thank you
Already Tried: I continually delete sent & deleted folders.