What is the best way to market my service to CEOs of companies with 25 employees or more?

You are missing whether LinkedIn and mailers are relevant to your target customers and also how they use these media, if your targeting was accurate.
- (Buyer Personas http://j.mp/1LPsR1a)

GOOD NEWS.
Many CEOs of small companies are active on LinkedIn and even write their own content, but I can't help you without knowing which sub-segments you could serve better than anyone else.

You can even use LinkedIn to rank CEO's and categorise them by industry, company size and frequency of use, along with other criteria.
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SELECTING A MARKETING MIX
The better tactical selection will depend on what type of companies your CEOs run, what they expect from a vendor like you and where your target customers are, even if this means websites, phones or apps.

CEOs could be more receptive if they thought that you understand their point of view better than anyone else. Perhaps you could get attention from active target members by commenting on their content, (LinkedIn and anywhere else they write) because marketing is about your target, not you.

MEDIA PLANNING
- (Media Planning http://j.mp/1EByAbz)

There are many other variables that will interact along your target's decision process, like influencers and competition. I will only comment, however, on your mix of LinkedIn adverts and a mailer.

1.
(LINKEDIN)
Your LinkedIn adverts could have been poorly targeted and designed, because you didn't learn your audience's media usage before hitting them. Perhaps your CEOs are more active elsewhere, like Twitter, Facebook or Clarity,
This is why I need you to elaborate on your target segments or I can research it for you.

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HACK!
If you've still got a list from the mailer, you can check individual names on LinkedIn and interact with them. It would be wise to get a premium plan, at least temporarily, so that you can contact decision makers directly.

You can still use the post office for thank you notes and seasonal greetings.
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2.
(MAILER)
If the purpose of your mailer was to generate sales leads, the list to which you sent your creatives should have been made of prospects who were most likely to be shopping, based on their past behaviour and not only on demographics, which is often the case when you buy a postal package, but do not control the list.

There are many things that could have gone wrong with your mailer and LinkedIn ads each by themselves and many more by combining them. You can't either expect one round of anything to build you an empire, because sales are built on reach and frequency.

3.
(OTHER MEDIA)
Have you thought of other media, like events?
- (Media Planning http://j.mp/1L9U2kw)

Speed counts. Your competitors could read this answer and get to your buyers first.

Your options are:
1. (SLOW!) Exploring the links above for content.
2. Calling me to start your next marketing plan.

What is your service? Are you hitting them with their pain points? Linked in works if you are relationship building first. You can sometimes get the email address from LinkedIn. If you are connected on LinkedIn try asking for a meeting to get to know them and their business. Call me for more tips.

It's about providing value to them.

You're right, likely your mailer never made it to their desk.

One of the nice things about LinkedIn ads is you only pay when they see it.

I think LinkedIn is a great starting point; but it is a process that cannot be automated. It is an investment of time to build a relationship and prove value.

I help entrepreneurs like you develop a strategy to accomplish goals like this. I'd be happy to discuss further. Book a call and let me know when you're ready to get started.

-Shaun

It really depends on the type of service you are selling. In general though, I like going the sweat equity route versus the paid route (at least to start) - you should look at this like building a machine, and before you build an entire assembly line you want to try to produce a few of your widgets (e.g. interactions/responses) successfully and then scale from there. So, keeping yourself connected to the channel selection, content crafting and ongoing metrics or results will be helpful so that when you want to drive scale (and have the sales dollars to invest in expanding paid marketing services) you know how to be more effective in that rollout.

A big issue with getting in front of these CEOs comes down to 1) gatekeepers and 2) timing of when they are in need of your services. The good news is that with the size of the organizations you are targeting (25+ employees as a start) the gatekeeper component becomes a little easier to navigate (with a little effort, connecting directly with CEOs of companies with less than say 200 employees is very feasible on scale.) The second part can present a much more interesting challenge. CEOs and business operators are busy folks, and dont typically have the time to think about anything other than the problems on their radar currently. So if they receive even great content or messaging related to something not on their current agenda, the chances of it being disregarding are much higher. Sending direct mail (or even a drip email campaign) can only be as effective as your guesstimate on when they may or may not be experiencing a pain point your service can solve. this is further complicated if they have a current contractor or partner who supplies the service you want to provide - so it's a function of hitting their pain point timeline but also their dissatisfaction period whereby they are open to alternative service providers.

The bottom line is that you have to work a solution that keeps you top of mind with your target prospects so that when those pain thresholds or dissatisfaction points are crossed they can recall your name/service. There are a myriad of ways to achieve this, plus other tactics that should be utilized (crafting targeted/consultative/solutions driven messaging, creating tools that will bring your audience to you such as white papers, blog posts, seminars or even some sort of automated online tool that helps their business.) Cracking the code for getting in front of your target market (especially these CEOs) can be complicated, but there is most definitely a manageable and scaleable process that can be achieved here. I'd be happy to connect and talk about your specific services and help craft a more targeted plan that can help you start seeing results quickly! Feel free to schedule some time and we can connect to discuss further.