Are there ways to test our messaging without spending a dollar on external validation?

You don't need to spend a dollar on external validation.

But you do need external validation. 

One of the things I remember from a Pragmatic Marketing course I took early on as a PMM was the term NIHITO -- Nothing Important Happens In The Office

• If you have customers, asking them for feedback will not cost any money
• You should also ask feedback from prospects, I generally use InMails to target 10-15 buyer personas. (Linkedin generally gives you the first month free)
• Analyst feedback is generally harder to get unless you pay them. That's ok - because customer and prospect feedback trumps everything.
• Finally, the best way to test messaging is to actually try selling with the new messaging. Start by collaborating with a few friendlies in the Sales team to pilot new messaging and see how prospects react. 

There's always a cost! 

• You can interview existing customers to validate whether proposed messaging resonates, but it's difficult to get validation at scale this way (certainly nothing quantifiable), and super time-consuming.
• You can A/B test proposed messaging in-market — on your homepage, for example — but there's opportunity cost for every visitor who encounters messaging that isn't a winner. Worse if you're testing with paid placements.

Survey-based message testing solutions are pretty affordable, and you'll know before you go to market which messages are winners and losers (or worse, if you really need to go back to the drawing board). Consider that the increased confidence up-front, and prospect of a more successful launch, might justify a small expenditure before you're putting money into content production and ad spend that might fall flat.

This is where the loss of conferences/events this year has been painful. One of my favorite ways to test messaging is to attend conferences, work the booth, and see how well different pitches land.

Another approach I've used is to test messaging through experienced sellers. When trying out some new messaging, I'll ask a couple senior sales people to try it out with discovery/intro calls. We'll collect their feedback, and listen to call recordings to get a sense of how well it's resonating.

Absolutely, there are a few ways to do so:

1. Social listening - Monitor social media and online reviews for customer reactions and feedback on the messaging.
2. Work with other departments, such as sales and customer service, to gather feedback from customer interactions and experiences.
3. Attend industry events and conferences to network with customers and gather their feedback in person.
4. Utilize free online forums and communities to gather feedback and insights from potential customers.

Many organizations have customer advisory boards or customer councils. These are great venues to validate messaging and even directly ask key customers how they view your message.

I generally work closely with product management and sales as I'm crafting messaging. Both organizatons along with product marketing spend a lot of time in front of customers.  

Yes, a few.

Actively, 

1. Your own customers or power users who are passionate about your products. Get them into a call and chat with them. Do this atleast 5-6 times with different customers.
2. If you have a reseller or partner network, then their sales and CSM teams can be tapped for validation
3. A validation test that you can run on your own website.
4. Your own sales and marketing teams.

Passively,

1. Participate in or listen to sales calls where the new messaging is being used in a preso or otherwise. Gauge validation based on customer's reactions or questions raised.
2. If your conversion flows are setup across channels, you can compare how the new messaging is doing vs. the old messaging in terms of conversion (whatever that might be).

Cheers,

Kash