Flagging of messages should be optional.

[alexandru-mng]

Expected Behavior
Flagging of messages should be optional similar with SearchTermStrategy

It would be ideal to simply bypass the default behaviour when a custom SearchTermStrategy is used.

Current Behavior
Messages are always flagged when the email server does not support \Recent or user flags even when that flag is not used when searching for new new messages.

How has this issue affected you?
Microsoft Exchange does not support \Recent or user flags, thus ImapMailReceiver always flags the read messages.

Are you aware of any workarounds?
I am not sure if this even works, but it may be a workaround.
https://stackoverflow.com/questions/62214324/java-mail-listner-this-email-server-does-not-support-recent-or-user-flags

What other alternatives have you considered?
Override ImapMailReceiver.setAdditionalFlags in order to remove the 'FLAGGED' flag, but this is not a viable solution because it may remove a "real" Follow-up flag.

[artembilan]

@alexandru-mng ,

if you see what can be done from the framework perspective, feel free to contribute the fix: https://github.com/spring-projects/spring-integration/blob/main/CONTRIBUTING.adoc.

I'm not sure yet what is going on, but will be happy to review PR.

Thanks

[artembilan]

Please, find the fix in the linked commit.

Thank you for the report anyway!