mutt remove white space in 67 character in the subject

[Bouzite, Radouan]

If I send an meail with mutt using the following  subject :
 "1234567890123456789012345678901234567890123456789012345678901234567
890"

I receive the email with the subjsct changed : the white space in
positon 67 was removed :

"1234567890123456789012345678901234567890123456789012345678901234567890"


My Mutt version  : 
Mutt 1.5.18 (2008-05-17)

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Radouan Bouzite
Unix/SAN Admin.
Ipex Management Inc.
Tel : (514) 769 3445 ext 291
Fax :(514) 769-1672