notify.smtp does not work with proton mail (login problem)

[greentux]

The problem

I get a
"reply: b'553 5.7.1 smart@box.li: Sender address rejected: not logged in\r\n'"

for the following config.

login credentials tested.

What version of Home Assistant Core has the issue?

2025.10.3

What was the last working version of Home Assistant Core?

No response

What type of installation are you running?

Home Assistant OS

Integration causing the issue

SMTP

Link to integration documentation on our website

No response

Diagnostics information

send: 'ehlo 5c53de3b-esphome.local.hass.io\r\n'
reply: b'250-mailsubosl1002.protonmail.ch\r\n'
reply: b'250-PIPELINING\r\n'
reply: b'250-SIZE 36480000\r\n'
reply: b'250-AUTH PLAIN LOGIN\r\n'
reply: b'250-ENHANCEDSTATUSCODES\r\n'
reply: b'250-8BITMIME\r\n'
reply: b'250 CHUNKING\r\n'
reply: retcode (250); Msg: b'mailsubosl1002.protonmail.ch\nPIPELINING\nSIZE 36480000\nAUTH PLAIN LOGIN\nENHANCEDSTATUSCODES\n8BITMIME\nCHUNKING'
send: 'mail from:<smart@box.li> size=339\r\n'
reply: b'250 2.1.0 Ok\r\n'
reply: retcode (250); Msg: b'2.1.0 Ok'
send: 'rcpt to:<goofy@box.li>\r\n'
reply: b'553 5.7.1 <smart@box.li>: Sender address rejected: not logged in\r\n'
reply: retcode (553); Msg: b'5.7.1 <smart@box.li>: Sender address rejected: not logged in'
send: 'rset\r\n'
reply: b'250 2.0.0 Ok\r\n'
reply: retcode (250); Msg: b'2.0.0 Ok'
send: 'quit\r\n'

Example YAML snippet

# email notifier
  - name: email_notify
    platform: smtp
    recipient: me@domain
    server: "smtp.protonmail.ch"
    sender: "sender_mail"
    sender_name: "My Home"
    encryption: starttls
    timeout: 20
    port: 567
    user: "login from proton website for app access"
    password: "hash from proton website for app access"
    debug: true

Anything in the logs that might be useful for us?

Additional information

No response

[greentux]

It seems, that HOAS does not start authentification...

[home-assistant]

smtp documentation
smtp source

[greentux]

user / username
my fault.