I'm working in a small company. We send our emails through company's mail server which is located (along with company's website) on a shared web host. Once in a while our Internet connection is down or the personnel have to wait a long time to upload their emails (with considerable size of attachments) to the mail server.
I would like to setup a local mail server and ask everyone to use this one instead. Then acting as a relay, this local mail server should relay emails to the one on the Internet (emails are always relayed to the same remote mail server). This way if our Internet connection is down, users can still send their emails to local mail server regardless and it's local mail server's responsibility to relay them once the connection is back up. And since it's a local mail server, it will take much less time for users to upload their attachments to it.
Here are my preferences / concerns (if possible):
- I would like not to register or assign a domain name (mycompany.com) or MX record for my local mail server. This mail server is not an open relay and its lonely responsibility is to connect to a singular remote mail server and I hope this requirement eliminates the necessity of a DNS.
- I've heard there are concerns regarding my emails to be labeled as spam if they are relayed this way. Which I definitely don't want it to happen.
- Perhaps one of most important points to make is security. What are the security issues in this scenario? And how should I tackle them?
So are my expectations reasonable? Can I do this? If yes I'll be really grateful if someone could direct me to the right path, what to read and how to do it.
ps. If it matters, I'm planning to use