CentOS | Sendmail
On occasion I've noticed that completely separate messages going through a common SendMail server may have very similar SendMail QIDs.
For example one message may have a QID of r5SGTeQb019223 and another may have r5SGTEQb019223 (the difference being the case sensitivity of the E).
Why is this? Is it just coincidence or are there specific rules that determine how these QIDs are generated and what they should be?