Gmail bounce message inactive inbox processed as Soft Bounce

[Alpha1]

Affected version

2.3.7

This common Gmail bounce message is processed as a Soft Bounce:

Action: failed
Final-Recipient: rfc822; xxx@gmail.com
Diagnostic-Code: smtp; 552-5.2.2 The recipient's inbox is out of storage space and inactive. Please
 552-5.2.2 direct the recipient to
 552 5.2.2  https://support.google.com/mail/?p=OverQuotaPerm 5b1f17b1804b1-4775d265d99si1629965e9.16 - gsmtp
Status: 5.2.2

While this is technically classified correctly as 552 (inbox_full), this is practically incorrect. This inbox is also inactive and should therefore be processed as a hard bounce. As gmail is the main email provider these days and therefore high impact, its a bounce message that should be taken into consideration.

It would be best to look for:
Diagnostic-Code: smtp; 552-5.2.2 The recipient's inbox is out of storage space and inactive.
And classify such bounce messages as hard bounce.

 

[Alpha1]

This one has really high occurrence. I'm getting CTS from manually processing these 'Soft' bounces.

 

[Alpha1]

To elaborate:

The text inbox is out of storage space and inactive does not match any of the entries in \XF\EmailBounce\Parser::$invalidMailboxStrings.

 

[Alpha1]

And some more information about this:

Inactive Google Account Policy - Google Account Help

A Google Account gives you Google-wide access to most Google products, such as Google Ads, Gmail, and YouTube, using the same username and password. An inactive Google Acco

support.google.com

Inactive = email not accessed for 2 years or more.

BTW: I recently did a test with 300k email accounts. XenForo did not catch 70% of the hard bounces.
40% of hard bounces XF does not catch are caused by this very issue. I reported the rest of the issues.