Not sure if this is DH or Mozilla Thunderbird related. ?!?!
Thunderbird (TB) 52.7.0 (32-bit)
I get error “Failed to connect to server …” after having successfully downloaded my emails from the Dreamhost (provider) POP3 account.
The fact that I could download the emails shows that the settings are correct.
I have 2 POP accounts at Dreamhost. Both react like that.
I didn’t change anything in the TB settings.
Nor did I on the server side.
The TB message started showing up some 6 months ago (after a TB upgrade?).
----- edit 20.07.2018 -----
I created 2 more POP accounts with a local ISP and Gmail. Both worked fine without subject Thunderbird error message. Hence, only DH accounts seem to produce this error message.