Failed to Send Emails From My Laravel Application Using Cpanel

I'm trying to send 2 emails when user will submit the contact form. 1 should be sent to the user email & the other should be sent to my own email. My .env file look like this:

MAIL_MAILER=sendmail
MAIL_HOST=smtp.gmail.com
MAIL_PORT=465
MAIL_USERNAME=m.s***********@gmail.com
MAIL_PASSWORD='************'
MAIL_ENCRYPTION=tls
MAIL_FROM_ADDRESS=m.s***********@gmail.com
MAIL_FROM_NAME="${APP_NAME}"

I'm sending the emails from controller like this:

dd($request->email);
Mail::to($request->email)->bcc('[email protected]')->send(new ContactSubmit($contact));

I'm receiving all the emails on [email protected] but not receiving on any other domain. dd($request->email); is showing me correct emails.

Before I was trying to send emails from my own domain:

[email protected]

But I was receiving this error in my inbox:

SMTP error from remote mail server after end of data:
    552 5.2.0 xkfupRYgo20R2xkfupkpjt :CPANEL: Access to this mail system has been blocked for xh******** due to spam activity. Spam was seen coming from this account, and possibly other scripts running in it. For help resolving the issue, see http://x.co/spamclean. Once the compromise has been cleaned, please contact customer support to remove the block.