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Empty MessageId in MailMessage returned by Pop3Client FetchMessage instance method

Aspose.Email version: (.Net)
Silimarly to this topic, fetch of the attached message from POP3 gives an unexpected empty MessageId. Same behaviour using MailMessage.Load from previously saved message (by calling Pop3Client instance’s SaveMessage method).

We’ve used that property for years to identify already saved email messages (for ImapClient too); starting from April 2020 this issue is affecting an increasing number of messages.
Please don’t just reply that UniqueId should be used, because:

  1. MessageId has never been deprecated for Pop3, nor for Imap
  2. ambiguity between UniqueId and MessageId has been partially addressed recently by updating an old doc page about Detecting New Email Messages on POP3 Servers, which again leaves Imap uncovered

Thank you,
email.zip (4.2 KB)


I have observed the issue shared by you and in order to proceed further with investigation on our end, I request you to please share the working sample code reproducing the issue that I may use to log investigation ticket in our issue tracking system.