Can't send mail via Google Workspace #5990
Description
Describe the Bug
I would like BookStack to send e-mail via Gmail SMTP relay (using my Google Workspace domain).
It fails intermittently, for example first click on "Maintenance->Send test email" works fine, the next one a second later fails. The same for invite e-mail to new users. The error message is:
production.ERROR: Failed to send user invite with error: Expected response code "250" but got code "421", with message "421-4.7.0 Try again later, closing connection. (EHLO)
Steps to Reproduce
Configure SMTP relay in Google Workspace according to https://support.google.com/a/answer/2956491
Configure BookStack to use Gmail relay:
MAIL_DRIVER=smtp
MAIL_HOST=smtp-relay.gmail.com
MAIL_ENCRYPTION=tls
MAIL_FROM=foo@example.org
Try to create a new user and send them invitation e-mail
Observe it sometimes fail with red error pop-up and "production.ERROR: Failed to send user invite with error: Expected response code "250" but got code "421", with message "421-4.7.0 Try again later, closing connection. (EHLO)" in laravel.log
Expected Behaviour
The mail sending should succeed 100% of time
Screenshots or Additional Context
- Google Workspace supports a few methods to send e-mails via them, SMTP relay being the preferred one according to https://support.google.com/a/answer/176600
- 421-4.7.0 is not specific for Gmail, it's their catch-all error code for "may be spam/unauthorized, try later" as per https://support.google.com/a/answer/3726730
- I have found a few people with the similar problem, e.g. https://help.nextcloud.com/t/started-getting-smtp-errors-from-gmail-relay/107694 and https://serverfault.com/questions/929559/postfix-error-421-4-7-0-try-again-later-closing-connection-ehlo
- Apparently Google does not like when connecting mail server does not introduce himself properly in HELO/EHLO, but just uses "localhost" or "127.0.0.1"
- I confirmed that with telnet:
$ telnet smtp-relay.gmail.com 587
Trying 142.250.110.28...
Connected to smtp-relay.gmail.com.
Escape character is '^]'.
220 smtp-relay.gmail.com ESMTP a640dd1662f3a-a38921cc907sm153220566b.83 - gsmtp
EHLO [127.0.0.1]
421-4.7.0 Try again later, closing connection. (EHLO)
421-4.7.0 For more information, go to
421 4.7.0 https://support.google.com/a/answer/3221692 a640dd1662f3a-a38921cc907sm153220566b.83 - gsmtp
Connection closed by foreign host.
$
$ telnet smtp-relay.gmail.com 587
Trying 142.250.110.28...
Connected to smtp-relay.gmail.com.
Escape character is '^]'.
220 smtp-relay.gmail.com ESMTP 2810306940e0a-594af1f2ac4sm256491fe81.0 - gsmtp
EHLO foo.example.org
250-smtp-relay.gmail.com at your service, [111.234.56.123]
250-SIZE 157286400
250-8BITMIME
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-CHUNKING
250 SMTPUTF8
- I confirmed with "tcpdump port 587 -s 0 -A" that indeed BookStack says EHLO [127.0.0.1] when talking to Google. Sometimes it works fine and email is sent, sometimes Google replies with error and sending fails.
- BookStack is served at foo.example.org, APP_URL is set to https://foo.example.org
- Editing getLocalDomain() in /var/www/bookstack/vendor/symfony/mailer/Transport/Smtp/SmtpTransport.php:132 from "return $this->domain;" to "return 'foo.example.org';" fixed all the problems so far.
- After a quick glance at SMTP RFC https://www.rfc-editor.org/rfc/rfc5321 it looks to me that while IP address may be allowed sometimes, using domain is always preferred if available. I guess most actual mail servers prefer that too. So I would appreciate BookStack using the domain from APP_URL while introducing itself to mail servers.
Browser Details
No response
Exact BookStack Version
25.12.1