If your domain registrar does not support DNS Management, you can use
NameCheap's Free DNS It will let you add the necessary DNS records.
Once you have registered for NameCheap Free DNS, just change the nameservers to the ones provided by NameCheap from your domain registrar's control panel.
You need to create two A records pointing to your static IP for domain.com and
www.domain.com
Also if the amount of mail is less you can use
sSMTP to send mail via GMail, which will give guaranteed delivery to inbox. If sending from your server, the mail may not reach the inbox and can go to SPAM or JUNK folders.