I'm trying to set up zimbra for a small business. Originally I planned on hosting our own email, but I've since read about some of the problems and think I may just configure each user to be able to download email from various external accounts (we have three separate companies with their own domains).
My question is two-fold.
1.) Do i need to set up a DNS server to do this? I don't particularly see why, but I'm not at my office and I just read something that implied that you do.
2.) In regards to running your own email server, will I run into problems with blacklisting? I read in a redhat article that you could use your isp's relay (smpt.comcast.net, for example) to avoid that. But is this simply referring to setting up accounts regulated by comcast (with standard email provider limitations), or am i using a username and password to be authenticated by comcast, allowing my outgoing email to be simply forwarded? I plan on purchasing a static ip if I go that route, in case that was going to influence the answer.
Also, using an ISP relay wouldn't change the headers in a way that people would think the mail came from the ISP account, would it?