NET
2 not to be easily shaken from your composure or disturbed by any kind of spirit or message or letter allegedly from us, to the effect that the day of the Lord is already here.
Darby
2 that ye be not soon shaken in mind, nor troubled, neither by spirit, nor by word, nor by letter, as [if it were] by us, as that the day of the Lord is present.
KJV
2 That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand.