email

My e-mail account says I am using 1.79 gb of data out of the 2.0 gb allowed.  I have deleted all but 6 e-mails and they do not have attachments or pictures.  Sometimes when people try to e-mail me, their e-mail comes back undelivered.  And sometimes I cannot send an e-mail out, I can never send an attachment.  I think it probably is because of the lack of data.  Any suggestions would be appreciated.