When I tried using Mew on Windows, I got stuck sending mail through the submission port.
Even when I wrote an email in Mew and sent it with C-c C-c, it froze at "Creating an SSL/TLS connection...". The smtpd log also showed something like "smtpd lost connection after STARTTLS from xxx".
Cause
I found information from someone who had already solved this and fixed it.
When using STARTTLS, specify both smtp-ssl-port and smtp-port.
Mew, TLS (STARTTLS), and SSL (SMTP over SSL) - https://griffonworks.net/nikki/archive/4413.php
After adding ("smtp-port" . "587") to mew-config-alist in .mew.el, I was able to send mail.
(setq mew-config-alist
'(
(default
(ssl-verify-level 0)
("name" . "Washi")
("user" . "Washi")
("mail-domain" . "Washi.example.com")
("smtp-server" . "Washi.example.com")
("smtp-auth" . t)
("smtp-user" . "Washi")
("smtp-ssl" . t)
("smtp-port" . "587") ;; <- これを追加して解決
("smtp-ssl-port" . "587")
("mew-smtp-auth-list" . ("LOGIN"))
("smtp-auth-list" . ("LOGIN"))
("proto" . "%")
("imap-trash-folder" . "%Deleted Messages")
("fcc" . "%Sent Messages")
("imap-user" . "Washi")
("imap-server" . "Washi.example.com")
("imap-auth" . t)
("mew-imap-auth-list" . ("LOGIN"))
("imap-delete" . nil)
("imap-ssl" . t)
("imap-ssl-port" . "993")
("imap-ssl-verify-level" . 0)
("signature-file" . ".signature"))
))
Me
People who copy an existing SSL setting (SMTPS: port 465) and change it to 587 will probably get stuck the same way I did. Thanks for the information.