Hi everyone! I have this behavior in my mail server with ISPConfig and I don't know how to solve it. When a MUA (thunderbird or outlook) connected trouth pop3 and the config not have tha option "let a copy of mails for x days" some mails lost. I see the logs of the mail account and I can see that client have 3 mail in the inbox, the MUA connected read mails but just 1 is downloaded and the others disappear form the inbox. The only solution enable the option "let a copy of mails for x days" but I think that it should not be necessary. Anyone has this happened before? Thank you for your help!
This won't be a dovecot configuration issue, it's completely driven by your mail client(s). You can likely track what happened in the mail.log file, as dovecot will tell you the number of messages retrieved and deleted per session (eg. 'Disconnected: Logged out top=0/0, retr=0/0, del=0/0, size=0'). So find a timeframe where you had this happen, and start looking through the logs ahead of that. The number of messages in your mailbox should increase with ever message delivery (which you also find in mail.log), and will decrease every time a client requests to delete messages (by the number of messages in del= entries). Look for things like having multiple pop3 sessions open at the same time, possibly from different ip addresses (multiple clients running). You might simply have some messages downloading on one machine and some on another, or it could be something else going on, but careful inspection of the logs will likely reveal what it is.
