My Cox Email has been migrated to Yahoo. I have configured the Network Configuration in PMail for Yahoo. I am using POP. I can retrieve/delete my email for my Cox Account on Yahoo.

I've generated an APP password for PMail.

I'm unable to Send (SMTP) from PMAIL to Yahoo. This is the Trace showing end of transaction. I've masked the sending and recipient email address in the trace.

Can someone tell me what I'm doing wrong in my configuration?

19:18:15.371: >> 220 smtp.mail.yahoo.com ESMTP ready
19:18:15.371: << EHLO [192.168.168.11]
19:18:15.402: >> 250-hermes--production-ne1-79ddd986d8-qbr42 Hello [192.168.168.11] [72.209.145.48])
19:18:15.402: >> 250-PIPELINING
19:18:15.402: >> 250-ENHANCEDSTATUSCODES
19:18:15.402: >> 250-8BITMIME
19:18:15.402: >> 250-SIZE 41697280
19:18:15.402: >> 250 AUTH PLAIN LOGIN XOAUTH2 OAUTHBEARER
19:18:15.402: << AUTH LOGIN
19:18:15.449: >> 334 VXNlcm5hbWU6
19:18:15.449: << amN1cnRpczEzQGNveC5uZXQ=
19:18:15.480: >> 334 UGFzc3dvcmQ6
19:18:15.480: << eWFwYWtreWRqY2VlemdxeA==
19:18:16.105: >> 235 2.7.0 Authentication successful
19:18:16.105: << MAIL FROM:xxxxxxx13@cox.net SIZE=436
19:18:16.293: >> 250 2.1.0 Sender xxxxxxx13@cox.net OK
19:18:16.293: << RCPT TO:yyyyyyy@gmail.com
19:18:16.324: >> 250 2.1.5 Recipient yyyyyyy@gmail.com OK
19:18:16.324: << DATA
19:18:16.355: >> 354 Ok Send data ending with <CRLF>.<CRLF>
19:18:16.480: >> 550 Request failed; Mailbox unavailable

Really appreciate any help that I can get.

Thank in advance!

First and most important: The log content you posted contains your username and password in an easily decodable form. I strongly suggest that you promptly change your credentials, especially if your username is your email address.

Second: You can see that authentication was successful so it does not appear that the problem is in the Pegasus Mail configuration. The final entry says "Mailbox unavailable". That tells you that the receiving email address can not receive the message. This error does not provide a clue into why. Can you send to other addresses?

Brian,

Thank you for your request and suggestion of changing my PW. I did that as well as adding 2FA. I tried my own Gmail email address, tried my brothers Hotmail email address and a friend's Cox email address. I get the same error for all of those. That's why I thought I might have something configured wrong in PMail.

That's sort of what I thought. But I know these are valid email address with valid mailboxes. Can you suggest anything else? Is there a more verbose log or can I turn on more verbosity for this log?

Thanks again for your response and help!

Here's a list of possible reasons for the error you got quoted from https://www.ionos.com/digitalguide/e-mail/technical-matters/550-requested-action-not-taken-possible-solutions/ which they call "the most popular ones":

550 requested action not taken: mailbox unavailable
550 user unknown
550 mailbox not found
550 relay not permitted
550 recipient address rejected: user unknown in local recipient table
550 reject due to policy restrictions
550 invalid address
550 user has too many messages on the server
550 permanent failure for one or more recipients

AFAIK, the internet session log is as verbose as it gets.

I just compared your log to one of mine and noticed that on mine, my 354 entry reads "354 OK<cr><lf>" and is followed by entries containing the headers and content of the message being transmitted. To me, the the entry"250 2.1.5 Recipient yyyyyyy@gmail.com OK" confirms the recipient and the entry "354 Ok Send data ending with <CRLF>.<CRLF>" is the request that Pegasus Mail start transmitting the data. At this point I am at the limit of my knowledge so don't know where to go from here.

Since we may need to start grasping at straws, something I would try is to test your configuration with the alternate port. If you are using port 465 with "Via direct SSL connect" try it with port 587 and "Via STARTTLS". I really don't expect this to make any difference since you are authenticating just fine; it's just something I would try out of desperation. I assume you have tried other desperation actions like restart Pegasus Mail and reboot the PC.

Couldn't it be a relaying issue, Brian? Especially given the fact of switching Network providers? A sender address mismatch of some kind?

If it is a relaying issue, I don't see it. Cox.net is switching to Yahoo services but based on my research, is maintaining the cox.net domain. The From: looks fine with the cox.net address.
https://www.cox.com/residential/support/coxnet-email-tr,ansitioning-to-yahoo.html

This article too (which I think is linked to in the one above):
https://help.yahoo.com/kb/mail/SLN36637.html

@mstrwiz, you have your cox.net address entered in the "My internet address is" field in the General tab of Internet Options right?

@idw, what else are you thinking?

First and foremost... Thanks to all that are willing to help!

Sorry I haven't been more responsive. I had to work today and am just now getting back to lookin at this.

I do have my Cox email address in "My internet address is" field.

The one thing that makes me believe it is PMail... is that fact that I get the same error whether sending to a valid Cox, Hotmail or GMail email address.

As suggested... I was originally configured for port 465 - Via direct SSL connect. I just tried port 587 - Via STARTTLS. I still received the same error msg.

One thing that would be interesting if someone is willing to spend a few minutes testing their using their PMail client, would be to setup a Test Yahoo email address and see if they can either "send successfully" or if that get the same error I get "Request failed; Mailbox unavailable."

I have searched for the 550 error msg and possible resolution.

This link is interesting:

https://stackoverflow.com/questions/50534061/smtpclient-request-failed-mailbox-unavailable

At the bottom of the link:

"Mailbox Unavailable" is a message from Yahoo's mail server, but means very little except that they didn't want to talk to you.

The "To:" address might be out of space or spelled wrong, or they might not like your IP address or any of a hundred other things.

You can google for yahoo postmaster help and see if they have any suggestions.

You have successfully connected but they refused to accept your mail. You would need actual information to know why.

Here's another page providing a list of possible reasons and solutions at https://www.siteground.com/kb/smtp-error-550/:

Error 550 – Variations and Solutions

550 Requested action not taken: mailbox unavailable
550 5.1.1 The email account that you tried to reach does not exist
550 5.7.1 Unable to relay
550 5.4.5 Daily sending quota exceeded
550 5.2.1 Mailbox cannot receive email
550 5.7.1 Message rejected due to content restrictions
550 5.7.1 Message rejected as spam by Content Filtering
550 5.1.10 Recipient not in directory
550 5.7.1 Message size exceeds fixed maximum message size
550 Message headers fail syntax check

And since we just had an issue with this I would like to check for the last one, i.e. a syntax error: In our last case there was an error with Pegasus Mail's "Date:" header due to invalid manually configured settings on Tools > Options > Advanced settings > SMTP time zone which could be fixed by enabling the "Auto" option, see https://community.pmail.com/index.php?u=/topic/12101/the-header-field-date-is-syntactically-not-correct/2#post-56774.

This is what I think is happening. I'm clueless as to why though.

Can you send to those addresses from the cox.net webmail interface?

I have reached out to a friend who had a Yahoo account. I don't know if he still does, but if so, I've asked for confirmation that he can send. I will let you know when I hear something.

I can send emails to Cox, Hotmail and Gmail via the web interface - just not outgoing SMTP via PMail.

I think there might be something configured wrong at Yahoo - but have no idea how I can communicate with yahoo email support.

I finally heard from my friend who has a Yahoo account. He is not having any problems with sending. I'm clueless what to suggest from here other then to turn to Cox for support. I don't think Yahoo support is the direction to go unless Cox give you a specific support contact handling Cox issues.

Thanks to everyone that replied and tried to help!! Appreciate it!!

I'll try to see if I can get Cox support to help with this issue.