Dovecot and Thunderbird 15

Hi, I recently had some issues with Thunderbird 15 when removing e-mail. With my other mailclient Outlook I could without any issue.

As I don't grand POP3 mail pickup, I disabled that in dovecot.conf

#service pop3-login { # inet_listener pop3 { #  address = 10.10.10.52 #  } # inet_listener pop3s { #    address = 10.10.10.52 #  } #}

Enabling the above and restarting Dovecot solved the issue. Is it TB related or do I overlook a config parameter? E.