Hello @tarator
thank you for add this information on doc, i search too for that.
I my side, i have found this command for escaped user and password if needed :
python3 -c 'import urllib.parse; print(urllib.parse.quote_plus("put_your_user_or_pwd_here"))'
On my side, i get already error for create user :
Aug 12 10:52:33 services gunicorn[1645175]: smtplib.SMTPAuthenticationError: (535, b'5.7.8 Error: authentication failed: UGFzc3dvcmQ6')
I have escaped my smtp user : user%40.domain.ndd
I have beautiful password without escaped need
I have test my account via echo "hello there username." | msmtp -a default username@domain.com
=> work well
EMAIL_CONFIG=smtp+tls://user%40domain.tld@:beautiful_pwd@domain.tld:587
=> not for funkwhale with good params ...