The visible length of subject lines varies by the device the email is viewed on but some email clients do limit the subject to a maximum of 255/256 characters, which may be the case in your example. Regardless, the viewing size of a users screen should be considered when altering the subject length as most devices will only show 50-70 characters before truncating or wrapping. If you have a lot of mobile users they are definitely not going to see the entire subject line in their inbox. What is the reason for the really long subject lines? I like the 50 character limit as it forces users to be succinct, the body text is where the detail should lie.
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