Mail sending is not working in Mozilla,please help

Hello I used this plugin for my Contact Form .
Its properly working ,Sending email in Chrome,Safari BUT , NOT sending mail in Mozilla Firefox.
Please Help me to sort out this issue, as tomorrow is project deadline.

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Link => https://linux.aress.net/ESCtNewWeb/environmentalservices/
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below label REQUEST AN ONLINE DEMO ,There is contact us form where i used your plugin.

Thanks in advance

https://www.ads-software.com/plugins/si-contact-form/