some mail with attachments are stuck in outbox. The do get send but they are not moved to SEND items. em Client sends it multiple times. Spamming our clients. PLEASE HELP!! I had phone calls from clients that are not very happy receiving mails 30 times.
Maybe open a support ticket through Pro Support. They are usually pretty quick to answer.
This is a long-time existing issue. Most likely related to slow upload speed. It would be great if eM Client can fix this.