Thanks for reporting. This should be now fixed in Smack 4.2.0-rc2-SNAPSHOT. Due the imminent release of Smack 4.2, this fix won’t go into Smack 4.1. I’d suggest that you consider updating to Smack 4.2.
Fixed with Don’t wait the reply timeout in OfflineMessageManager.getMessages(Lis… · Flowdalic/Smack@b5415fe · GitHub