If you draft a post and see a "Post too long for email" message, this means that it just may appear as clipped or truncated in a reader's email inbox.
While there isn't a word count or length restriction on Substack posts, some email providers like Gmail will truncate messages exceeding 102KB. You'll see this message in the post editor after you've exceeded Gmail's size limit.
You'll still be able to publish the post.
Tip: If the newsletter is truncated in an email, readers can click on "View entire message" and they'll be able to view the entire post in their email app.