Email sent date

If a sent email is provided in eml format, and the same email is provided again at a later date but from a different source computer having being imported from the original computer, is there any reason why the sent date of the email would change by a few minutes or should the sent date of the email always be the same?

RFC 5322 defines the origination date (i.e., the “Date” header field) as follows:

The origination date field consists of the field name “Date” followed by a date-time specification.

The origination date specifies the date and time at which the creator of the message indicated that the message was complete and ready to enter the mail delivery system. For instance, this might be the time that a user pushes the “send” or “submit” button in an application program. In any case, it is specifically not intended to convey the time that the message is actually transported, but rather the time at which the human or other creator of the message has put the message into its final form, ready for transport. (For example, a portable computer user who is not connected to a network might queue a message for delivery. The origination date is intended to contain the date and time that the user queued the message, not the time when the user connected to the network to send the message.)

Based on this definition, since subsequent imports or otherwise processing of the message should not alter the date and time the message’s creator had deemed it complete and ready for transport, I wouldn’t expect the origination date of an already sent email to change.

A potentially innocuous reason for such a change might be an improper conversion between email formats.