Robot gets stuck on mail activity

I have some workflows which uses various mail activities, like read pop3 messages and send smtp mail message. The mail account is an office365 account. Sometimes the robot gets stuck on these activities. They do not fail or time out, but just hangs at the mail activity. When this happens I have to restart the server the robot is running on, and then it works just fine for a while. Does anyone know why this happens?

Hi @hLien

Usually how many mails are you processing at a give point? Just trying to figure out a causeā€¦ :thinking:

I have tried various number of mails, and it seems that this is not the cause, as it fails with only one mail.