IMAP-auth on LAN and otherwise

B. Reino reinob at
Wed May 3 18:27:02 EEST 2017

How? :)

On May 3, 2017 5:25:51 PM GMT+02:00, Rupert Gallagher <ruga at> wrote:
>Problem solved.
>Sent from ProtonMail Mobile
>On Tue, May 2, 2017 at 3:46 PM, Rupert Gallagher <ruga at>
>Thunderbird has been bugging us with connection errors. Dovecot is
>installed on a local server that carries a local IP and a public IP.
>When Thunderbird on a local client connects successfully, Wireshark
>shows a SYN request from the client's IP on LAN to the public IP of the
>server, followed by the ACK from the same public IP. When Thunderbird
>on the same local client fails to connect, Wireshark shows a SYN
>request from the client's IP on LAN to the public IP of the server,
>followed by the ACK from the server's LAN address, the client does not
>accept the ACK as valid and sends a new SYN request. The loop
>eventually leads to time-out. At the client's console, the DNS query of
>the IMAP server always responds with the server's public IP address.
>It is evident from Wireshark that the dovecot server sends ACKs from
>two IPs. Is it possible to instruct Dovecot to use the public IP only?

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