Will people understand what you’re trying to say? It’s usually better to avoid topics (or opinions) that are complex if many people are extremely passionate about them. For example, sharing almost any opinion about immigration policy is usually a bad move, unless your audience is unusually homogenous. You could agree 99% with someone and still piss them off by using the wrong term just because they have such a strong “either you agree 100% with us, or you’re our enemy” mentality. I once pointed out that I think it’s unacceptable to capture and torture people for years—especially if they aren’t charged with any crime, there’s no evidence they’ve done anything wrong, and they’re children. I got several emails back from people saying, “you have no idea what you’re talking about” or “you should stick to marketing and leave politics to people who understand it.” They took it as commentary on geo-politics. I just said I’m not okay with pointless torture of children. I thought we’d all agree on that.
People buy when they feel that they have good reasons to do so. So, you need a strong value proposition (=great reasons for buying what you sell). If you don’t have it, you can’t be able to give people good reasons for buying. If you don’t know what—specifically—would make people see value in your offer, how could your email marketing (or any marketing) be effective?
Genuinely effective campaigns segment the market as carefully as possible, and target accordingly. Relevancy is key for getting people to open emails and respond to your CTA – but what's ‘relevant' differs from person to person. If you're going to make your emails as relevant as possible to everyone who reads them, you need to Segment, Target, and Position.
A trigger can also be a passive customer behavior, such as not opening your last few emails, not logging in to use your service for a while, or downloading a product without downloading the tutorial or an important related resource. These types of drip campaigns can help re-engage customers who were moving through the customer lifecycle but have somehow gotten “stuck.”
A significant element of email marketing is relationship. Does a recipient trust you? Does a recipient even know who you are? When an email jumps the gun by forcing familiarity too soon, the personalization comes across as skeevy. Intimacy is earned in real life, and it would appear to be the same way with email. Take this example from my inbox; no one has called me lowercase kevan l lee in years.
Are you willing to alienate people who disagree with your opinion? Sure, not everyone who disagrees with you will unsubscribe. But if you can’t take the risk of alienating a large portion of them, it’s better to avoid the topic. The only exception are friendly disagreements. For example, it can be a good idea to show your support for a specific sport team, even if you know many in your audience like another team. As long as they don’t take the sport very seriously, it can be just a fun thing to talk about. I could, for example, tell that I’m more of a dog person (we have two dogs) than a cat person. I have nothing against cats, but I like walking with dogs. I doubt almost any cat person will hold that against me.