Must an oath of "by Allah" that came in an email be fulfilled, even though it was uttered unwillingly?

A Muslim must consider the content of the message. If it contains falsehood or sin, it is not permissible to send it to others, and he is obligated to offer expiation for his oath if he had sworn to send it. However, if it contains useful things and beneficial advice, it is commendable to send it with the intention of spreading goodness. In general, an oath must be fulfilled unless it involves a sin; otherwise, expiation for the oath becomes necessary. If the oath was uttered without the intention of swearing, it falls under a thoughtless oath (laghw al-yameen), for which there is no accountability.