Fast way to get seen flag of a message

Question

When calling GetMessageInfo(uid) the Flags collection is not populated, requiring me to call GetFlags(uid). This call is very expensive, consuming a significant amount of time and data transfer. Is there a better way to see the seen status of a message?

Answer 1

Imap.GetMessageInfoByUID retrieves several IMAP parameters including flags.

Those parameters are as follows: RFC822.SIZE, INTERNALDATE, FLAGS, ENVELOPE, BODYSTRUCTURE and in case of Gmail: X-GM-THRID, X-GM-MSGID, X-GM-LABELS.

To diagnose this further, please turn on logging:
https://www.limilabs.com/blog/logging-in-mail-dll

If the flags are not in the server response there is nothing you can do - you must use GetFlagsByUID(List uids). Make sure you are using the overload with uid list as argument. Retrieving data in bulk is generally much faster, then invoking this method for every uid.