It's worth checking whether you're running IPv6. It does become very relevant. e.g., SPF records need to include it, it must also have a good rDNS, etc.
In particular, I know gmail hold IPv6 to higher standards. Some things (e.g. rDNS) that we traditionally treat as 'should', gmail will treat as 'must' over IPv6 - it's being treated as a chance to drop a lot of legacy leeway.
I do run my own MTA. It's not high-maintenance, at all. Understand the pitfalls, iron them out, and then stick with it to build your reputation. There is no magic bullet - the big providers won't tell us how they measure us - the best we can do is be well-behaved, stay well-behaved, and adopt modern standards (TLS, SPF, DKIM, etc) as they're thrown at us.
My best advice is to choose a reputable host. There's a lot of race-to-the-bottom in the web hosting market, and VPS are turning out no different. Keeping a clean house is good for your reputation - but so is living in a nice neighbourhood. It's well worth a couple of bucks extra to find such a neighbourhood.
This sucks big time. We should be able to send email from fucking home, not beg an external, bigger guy to either do it for us (one's ISP, google…), or lend us a machine so we can do it from there (Amazon, OVH…).
Email providing is so concentrated right now it is starting so show signs of network effects —just like more recent (anti)social networks. This is not right.
What I mean is, the originating IP address should not be such an overwhelming criterion of spamminess. When I receive spam, my most important criterion for filtering it is pure content.
I have a hard time believing spam is such a huge problem we have to use simplistic filters such as IP bans to deal with them. My email address is written without obfuscation in the open web (my own website), and my email clients' filters (Thunderbird or Evolution, depending) are more than enough once I have trained them a little.
(My domain is probably even less famous, but I do receive cold, non-spammy email from time to time regarding my blog articles.)
I am referring to how the big players (Google with Gmail, Microsoft with Hotmail, and I suspect many others) tend to flag as spam, or even outright reject your email, as soon as the IP comes from a "little player", such as residential IP, or even virtual private hosting IPs.
Sending an email to a user of such networks has become difficult —at least, more difficult than it should be. Unless of course you come from one of those huge networks. And of course, the users themselves don't see any problem with this: they assume that if you can't send an email to them, the problem must be on your end —not, say, Gmail's spam filter.
On the other hand, if everyone had a little box that send email directly from home, nobody would ever dare to block them.
"what he said". The Mail Transfer Agent (e.g. postfix, exim, etc) is the part of a mailserver that accepts mail, hands it off to a delivery agent if it's local, or hands it off to the recipient's MTA if it's not.
Basically it's the component that handles SMTP. Local delivery, pop3, imap, etc are almost always handed off to another component.
It's usually the difficult component because it's the service that other hosts will interact with. So if my imap service misbehaves, it annoys me until its fixed. If my MTA misbehaves, it's a lasting black mark against my host's reputation.
In particular, I know gmail hold IPv6 to higher standards. Some things (e.g. rDNS) that we traditionally treat as 'should', gmail will treat as 'must' over IPv6 - it's being treated as a chance to drop a lot of legacy leeway.
I do run my own MTA. It's not high-maintenance, at all. Understand the pitfalls, iron them out, and then stick with it to build your reputation. There is no magic bullet - the big providers won't tell us how they measure us - the best we can do is be well-behaved, stay well-behaved, and adopt modern standards (TLS, SPF, DKIM, etc) as they're thrown at us.
My best advice is to choose a reputable host. There's a lot of race-to-the-bottom in the web hosting market, and VPS are turning out no different. Keeping a clean house is good for your reputation - but so is living in a nice neighbourhood. It's well worth a couple of bucks extra to find such a neighbourhood.