[stunnel-users] Re: Unexpected socket close while sending mail

On Thu, 22 Jul 2021 15:35:56 -0000 zfefm@gmx.de wrote:

But as soon I want to send a mail my mail program tries for 10-15s to send an then gives up.

[...]

protocol = smtp

[...]

I get exactly the same problem with Mac OS 10.9 and Thunderbird as email client. The above post was with OS 10.6 and Appelmail. So the problem seems to be on the stunnel (config?) side.

Hi,

"protocol = smtp" on client service implies STARTTLS command and, so, implies response from server accordingly to start the TLS session.

Are you sure that strato.de servers offers plain text and TLS upon requests via STARTTLS?

Otherwise, remove the protocol line or comment out with a semicolon (;)

https://datatracker.ietf.org/doc/html/rfc2487

Regards.