Question : Public IP address change can no longer send external email

I recently had to change ISP's.  Initially after the change sending and receiving external mail worked.  DNS servers were updated a few hours after I tested the sending and receiving and now I cannot send external email.  I host the company webpage and it is still not accessible.  I did a dns test at dnsstuff.com and it looks like things are pointing to the new ip address.  Any suggestions?

Answer : Public IP address change can no longer send external email

If you can't send it is more likely to be that you have not configured reverse DNS.  DNS changes can take up to 48 hours to completely propogate.