I happen to run a small company with a website built in PHP and I get several generic emails every couple of days from random individuals and fly-by-night "SEO consultancies", claiming that they "found issues on my website", "could help optimize website", "get us reach top Google positions" etc.

Most of this is auto-generated junk based on some keyword scrapping, but given the volume of it, I don't think it's possible to be taken seriously in that niche anymore.

I also get several "personalized emails" per week peddling software developers for hire, management trainings, factories in China, real estate investment opportunities and countless other junk, so I wouldn't count on that channel either. Anything that looks like a cold email goes straight to trash simply due to the volume of it.

IMO, a much better strategy would be to publish articles showing your expertise (i.e. comparing similar technologies, or sharing step-by-step instructions on accomplishing some familiar task), while mentioning that you do consulting in that area. People usually don't mind if you share them on Reddit/Linkedin/Twitter/HN and that can get a you a much better traction than cold-mailing people.