What are best practices in scaling up an outsourcing company?

Great question! I love questions like this ones.
First off forget about Silicon Valley. If you are not here with that sort of relationship you will spend a lot of resources before you make something sustainable here.
Second, you mention you've had some success - ok, why aren't you simply making that effort that has worked more efficient and thus grow that effort scale to in return scale up your success rate?
Emails are for long term nurturing not for quick generation. What I would suggest is first never show up empty handed, when you do make contact with one agency, know what they do and who for, offer directly related solutions for 1 client only. If you do a good job there they might build the relationship on their end.
With that said, don't pitch for long term pitch for an opportunity to save money or time or etc once.
Sorry but I gotta go, short reply.
If you have any further questions let me know :)

Today in this world full of promoters, the scaling up should not be much difficult.
I request you to spend a time to prepare a bunch of highly demanded strength of network partners.
Then ask them today's invaluable question
What makes the profit to you by subjective relevance to prepare a change in existing mode of delivery to a modest and design oriented technology based on your startup concepts. People will love such questions.
To people who regard the environment of highly situational the concept of asking right questions to solve their problems indulges in giving a priority upon opportunity
Though I do not have industrial contacts I have a great knowledge and wealth of information on how to approach specific client requirements.
Saying this I want to propose five different approaches
Do not overutilize the time information through the internet
Try to partner through correspondence of overly related impenetrable subjects
Use your valuable time effectively in trying to bring a five service, sales, implement, gather and repeat
Do not indulge in asking questions related to business partnerships upfront but instead, try to answer their problems using your solution. Then upon successful interaction and service delivery contact them for further modest implementation for future projects
Upon their satisfaction recommend them to your sales pitch to process

If you like to correspond further contact me through Clarity.fm
Thank You
With regards,
Karnati Kiran

It's simple: You need to be where these companies are. What magazines and blogs are the decision makers reading? What social media sites do these decision makers use every day? This is pivotal research that must be done first. Then, you can provide advertisements and marketing tactics in the channels that these people use.

I would blindly guess that maybe some print or online ads, as well as LinkedIn leadership articles and online ads could possibly be effective. Look at what trade shows these companies attend and find out how much it would cost to sponsor one of those events. There are many things you could do.

If you have questions or would like help with these tasks or if you'd like a free project estimate, please contact me!

Grow smarter by intelligently knowing how and when to outsource parts of your business. One of the least understood tools available for growing your business is outsourcing. It allows you to expand capacity without having to formally hire large numbers of new staff; without having to invest in new capital equipment, without leasing a larger commercial space; and without having to invest in development costs for non-core parts of your business, increasing your fixed overhead. To be clear, outsourcing is when you take a function, activity, or need of your business and hire an outside company to do the work instead of doing it in-house.
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath