From "The Email Design Best Practices You Need to Know"

Your email subject should be something that grabs your constituents’ attention and gets them interested enough to keep reading.

Make your subject line informative so that it offers something of value, but not so long that it gives away too much or reduces your readers’ interest. The ideal email subject should be a good, interesting summary that tells people what they can expect from reading your email in the fewest possible characters. 

Remember, your email subject isn’t the only thing a constituent sees when they see your email in their inbox. The other elements likely to show up are your name (or the sender’s name) and a snippet of the beginning of your email. Those elements are also important when it comes to getting constituents to actually read your emails.

You may choose to keep your “From” name the same throughout all of your emails for consistency, or consider using that opportunity to get even more specific about what constituents can expect from your email. 

Keep in mind that the sender’s name field should always include your brand name or something recognizable so subscribers know exactly who sent the email, and that it’s from a sender they trust and subscribe to. Then, the first line of your email can be another opportunity to pique subscribers’ interest about what your email has to offer.