Hello! I was wondering if remote content from email’s can affect the server its hosted on in anyway, I always see the thunderbird warning but have no idea why it is there.
The server software is generally not processing the contents of a message. It does do some verification of the contents, such as hashing, but the tools used are very mature and popular, so any security issue at this point will be difficult to discover and highly valued.
With regards to malware from remote content, that will be something related to clients. That information does not go through the server.
Ah, Alright. I was like wondering why that remote content always popped up! Thanks 
Because if the content is malicious, you could infect the device you are opening the email on.