Email is not instantaneous, although we expect it to be. The following article on Ask Leo! explains some of the problems that can cause email delays '''Why is some email to me delayed by days?''' http://ask-leo.com/why_is_some_email_to_me_delayed_by_days.html The article mentions that the message header information can help to determine ''where'' and ''how long'' the delays took, but unfortunately NOT the ''reason''. One delay that this article misses, is the '''polling''' interval on the email account. If the mail arrived at your inbox on the server, and you have just checked for messages, you may have to wait for the next interval to 'Poll' for new messages again. Although Thunderbird can set the poll interval as low as every minute, your email provider may require five or ten minutes between new message checks. Usually the more popular mail servers allow a more frequent interval, but they can easily become overloaded at busy times. TB-38.3 Win10-PC