Company sends me an email to my gmail.com account.
I open the email in my gmail account. It turns from bold to grey, showing it has been read by me. I do not reply to it.
Can the company gauge my IP address when I clicked on their email and opened it in my gmail account?
They may be able to tell that you have read it, but they shouldn't be able to get your IP address. Since 2013 Gmail has proxied images through their own servers, so "tracking pixels" will only get the IP of the Gmail server. This only applies to the web client though (and I believe Gmail's official smartphone apps do this as well, but I haven't tested). If you're using a 3rd party IMAP client then it may reveal your IP address when loading images.
Note that if you click on any links in the email, they can get your IP address no matter what client you use, unless you check the link destination first and verify it's to a domain that you trust and not a tracking domain.
No. The sender of the email can't see anything that is happening inside your inbox.
An email may ask to send a "read receipt". If sent, that will let the sender know the email was opened. It still will not reveal the IP address of your computer.
Yes they can get to know your ip address with HTML emails by including a request in img tag. This is how email trackers work to check whether users have read an email or not.
But in case of gmail they proxy the request so the ip will be of google servers.
