debugging a curl request / what would be the curl request to test whether a given username / password is working against a speciific smtp server

Question

I have a customer using a specific app that uses secure smtp to connect for outgoing email. I have a suspicion that it somehow got changed (whether by them or by the hosting provider is irrelevant). I would like to verify that their outgoing server auth's correctly via curl. I had no had in creating this system. I tried this:

at Apr 18$ curl smtps://outbound.att.net:465 -v --mail-from "[email protected]" --mail-rcpt "[email protected]" --ssl -u [email protected]:ourpassword

but get this cryptic error message:

* Rebuilt URL to: smtps://outbound.att.net:465/
* Hostname was NOT found in DNS cache
*   Trying 67.195.15.5...
* Connected to outbound.att.net (67.195.15.5) port 465 (#0)
* TLS 1.2 connection using TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
* Server certificate: smtp.mail.att.net
* Server certificate: Symantec Class 3 Secure Server CA - G4
* Server certificate: VeriSign Class 3 Public Primary Certification Authority - G5
< 220 smtp.mail.att.net ESMTP ready
> EHLO jonathans-MacBook-Air
< 250-smtp.mail.att.net
< 250-PIPELINING
< 250-SIZE 41697280
< 250-8 BITMIME
< 250 AUTH PLAIN LOGIN XOAUTH2 XYMCOOKIE
> AUTH LOGIN
< 334 VXNlcm5hbWU6
> dGhlbmV3YW9jQGF0dC5uZXQ=
< 334 UGFzc3dvcmQ6
> SWxvdmVjaGVlc2UwOQ==
< 535 5.7.0 (#MBR1212) Incorrect username or password.
* Authentication failed: 535
* Closing connection 0
curl: (67) Authentication failed: 535

thx for any help.

Answer 1

Short answer:

Wrong auth method

Longer answer:

The clue is the line that says Authentication failed: 535. While this could mean wrong username/password, this is not necessarily the case. It basically means that the method used to encrypt/hash the username and password produced a string that did not line up with what the mailserver had in their records. If the username and password is correct, then the most common cause of this is not taking into account the use of SSL/TLS or similar schemas.

Note:

For some reason, if an account is suspended for some reason, the same error message is used. I find it odd that they didn't come up with a different error code for "account not active" or something like that. You might want to check up on the status on the account first, just to be sure.