Rule of thumb, back up all business related emails with another form of communication to ask whether your intended recipient got it or not - telephone or SMS iow.
Also, get a decent hosting account with your own domain through a reputable hosting company that doesn't use SAIX ! - well worth the monthly cost, as ISP emails are usually crap - I won't touch my telkom ADSL account with a bargepole, mainly because I know thier email servers are sh1te.