Extending Case Comments for Outbound Emails
My organization would like to send an email with more than 4,000 characters through E2CP, but the current Salesforce limitation of case comments is 4000 characters.
The 4000 character limit of Case Comments is set by Salesforce and cannot be directly increased.
That said, if your organization would like to send comments longer than 4000 characters please refer to the Email to Case Premium Enhanced Comment Editor.
When the Enhanced Comment Editor is enabled for the New Comment page, Email to Case Premium populates a field called Most Recent Public Comment (HTML) upon Save/Send. This field is able to hold up to 32,768 characters.