Email issues - please advise
I work for a company and our accounting system runs on a Linux server. We recently 'upgraded' the accounting software to be able to send emails. Now from what I am told the server uses Sendmail and relays it through our ISP SMTP server. The problem is that when it hits our offsite/outsourced IMAP email server the email is outright blocked because the server sees that our server is an unregistered email server relaying through our ISP and it doesn't even make it to the spam filter. I would like to avoid the cost and maintentance required to upgrade our server to a true email server with all the right keys in place. Is there any way to have the server direct connect to the smtp server and send the email like Outlook (Sorry for using the devils name on this forum) would?
Any advice or explaination would be appreciated. I don't know anything about servers, nor did I want to learn because I was relying on another company to setup our server correctly. So unfortunately this is all the information I have. So please advise.