`550 Invalid server token` if RCPT_TO starts with custom_return_path_prefix

[yogesum]

If I am sending mail with domain example.com with custom_return_path_prefix as email then any recipient starting with email. fails with code 550 Invalid server token.

Example mail: return path domain email.example.com

RETURN PATH: <wazup@email.example.com>
MAIL FROM: <support@example.com>
RCPT TO: email.otherdomain.co.in
// => 550 Invalid server token

Note: Relevant piece of code code

Also, RegExp check similar to above is also done here

[willpower232]

Have you added otherdomain.co.in to your Postal server?

[yogesum]

No, It is someone else's mail receiving server. Receiver email is like someone@email.iimcal.ac.in

[willpower232]

I don't think Postal will let you add someone elses domain name onto an address in the email headers, Postal has to know about all the domain names that go through it.

[yogesum]

I am already sending mail to other email addresses. but when I send email to someone@email.iimcal.ac.in it fails.

I think fault lies in this code which check the rcpt_to using regex to ensure it is not return_path. It is wrongly classifying mails being sent to address someone@email.iimcal.ac.in as return path.

rcpt_to = data.gsub(/RCPT TO\s*:\s*/i, '').gsub(/.*</, '').gsub(/>.*/, '').strip
uname, domain = rcpt_to.split('@', 2)
uname, tag = uname.split('+', 2)

# Postal.config.dns.custom_return_path_prefix = 'email'
if domain == Postal.config.dns.return_path || domain =~ /\A#{Regexp.escape(Postal.config.dns.custom_return_path_prefix)}\./
  # This is a return path

[willpower232]

Sorry I misunderstood your issue.

Can you show us exactly what you set your custom_return_path_prefix to? How are you sending messages?

Is there any particular reason you set your custom_return_path_prefix away from psrp?

I am unable to replicate your problem BUT I do see some slightly weird behaviour in that Postal thinks all email with the return path prefix at the start of its domain name is a returned message.

Edit: as in earlier messages, this treatment is potentially erroneously applied to other domain names not known by Postal

[yogesum]

• postal.yaml settings

custom_return_path_prefix: email

• psrp to email was done for mailed-by: shown in gmail show details
• Emails are being sent over SMTP by CakeEmail of cakephp

Error can be reproduced for default setup of postal in which custom_return_path_prefix is psrp over telnet

User input starts with >

telnet
telnet> o mx.postal.domain.com 25
Trying xxx.xxx.xxx.xxx...
Connected to mx.postal.domain.com.
Escape character is '^]'.
220 postal.domain.com ESMTP Postal/QS6BKJ
> EHLO localhost
250-My capabilities are
250 AUTH CRAM-MD5 PLAIN LOGIN
> AUTH LOGIN
334 VXNlcm5hbWU6
> base64(org/server)
334 UGFzc3dvcmQ6
> base64(password)
235 Granted for org/server
> MAIL FROM:<test@domain.com>
250 OK
> RCPT TO:<yogesh@psrp.gmail.com>   
550 Invalid server token

[willpower232]

OK I can replicate and I have verified that is the piece of code causing the issue.

This seems to be a complete block SMTP only which calls into question why that particular bit of code is there. Using the API, the UI is incorrect but it still sends.

It might be handy to have some feedback from @adamcooke or @catphish on this one as it certainly affects a big bit of the system.

For now, you could try using the API client since CakePHP is composer-friendly (https://packagist.org/packages/postal/postal) or switching back to psrp. Could you send a screenshot of the bit in Gmail that you were trying to avoid? I couldn't spot it in mine.

[yogesum]

[adamcooke]

The custom return path prefix should be unique and not likely to be used. Postal needs to take responsibility for this domain. In our installation we use psrp as our prefix as we know we won't have any domains that start with that. In fact, that's the default.

[yogesum]

@adamcooke Problem is when we send email to some external host with subdomain same as psrp it will fail. Like sending email to address yogesum@psrp.gmail.com or yogesum@psrp.yahoo.com fails.