Would blocking emails from being used on a form lower rankings?

Hello, all.

I am doing some SEO work for a company and they mentioned that they get a lot of leads that are just not good quality for them (they are a B2B company and only deal with large volumes) from personal email accounts (like gmail and yahoo).

They mentioned their sales reps waste a lot of time going through these leads and wanted to see if I had any ideas to improving this.

The first thing that came to mind was simply blocking all personal emails and only allowing business emails in order for the form to be submitted. I didn't think much of it as I was not sure just how many of these "unqualified leads" they were getting.

The conversion rate dropped about 1.5% and total conversions were down - but everyone was happy. I just cut down on the time sales rep were rummaging through leads looking for a good one. Quality of leads sky rocketed.

This was about a month and a half ago. About a week ago our ranking starting falling. Ranking has consistently been going down for their website for the past 6 months and we are in the process of completely revamping it as it is out dated. However, it rank was falling faster than the trends of previous months.

The form rule was the only major change I made to the website, apart from a few non competing blog posts.

Would the form rule and drop in conversions have impact on their rankings?

Thanks