SMTP with Yahoo: Connection unsuccessful: SendMail: 550 Request failed; Mailbox unavailable - undefined

[Delawen]

Summary

I am trying to use yahoo SMTP to send emails.

Steps to reproduce

Configure a basic free Yahoo email on the SMTP settings and test it ("Test Connection"). See my configuration on the image below.

An error will be shown (mine in Spanish):
Connection unsuccessful: Connection unsuccessful: SendMail: Error ajuste "Dirección Desde", 550 Request failed; Mailbox unavailable - undefined

Which may translate to:
Connection unsuccessful: Connection unsuccessful: SendMail: Error in settings "Email from", 550 Request failed; Mailbox unavailable - undefined

Expected behavior

I should be able to send emails using that SMTP.

Observed behavior (that appears unintentional)

Possible fixes

Could be this? https://stackoverflow.com/a/51084780/469932

[Delawen]

The config.json file had a different "FeedbackEmail" and that confused my configuration. Would be good to add this to troubleshooting or a warning on this page to check that.

Thanks rubber ducks! I will close but not remove in case someone else has the same issue.

[sphuber]

Just want to report that I think I experienced a similar problem. I setup a Mattermost server with v5.30.1 and configured my SMTP server details but got the following error:

Connection unsuccessful: Connection unsuccessful: SendMail: Failed to close connection to SMTP server., 550 5.2.0 Spam message rejected

Setting the key EmailSettings.FeedbackEmail to the same value as that of EmailSettings.SMTPUsername fixed the problem for me.