[Discuss] Need help with undelivered mail.

[David Kramer]

I am having trouble sending mail to GMail accounts, and I'm getting 
inconsistent explanations. I could use some help figuring out the real 
cause.

Setup: I have a mail server running on Linode running 
postfix/dovecot/clamav/etc ( I successfully moved mail off my home 
server about a year ago).  I have Verizon FIOS at home.  I use 
Thunderbird for email on my main Linux computer.

When I send email to a gmail account, I am getting:

host aspmx.l.google.com[2607:f8b0:400d:c0e::1a] said:
     550-5.7.1 [2600:3c03::f03c:91ff:fe62:5ea] Our system has detected 
that this
     550-5.7.1 message does not meet IPv6 sending guidelines regarding PTR
     records 550-5.7.1 and authentication. Please review 550-5.7.1
https://support.google.com/mail/?p=IPv6AuthError for more information 550

The link that goes to HAS ABSOLUTELY NOTHING to do with IPv6, it has to 
do with bulk emails.  What I *THINK* it means is I need to set up IPv6 
records, but I'm not sure which ones.

But then I do MORE googling about that error message, and some pages say 
550-5.7.1 *IS* about spamming and blocklists and this has absolutely 
nothing to do with IPv6.

According to 
https://mxtoolbox.com/SuperTool.aspx?action=blacklist%3athekramers.net&run=toolpage 
my IP address is on the SORBS DUHL list and the Spamhaus ZEN list. 
Digging into Sorbs and https://www.spamhaus.org/pbl/query/PBL1637778 I 
get the impression my whole IP range is blocked because outgoing mail 
should go to smtp.verizon.net when I'm at home.  But if that's the case 
how does sent mail get saved to my IMAP server?? Is it sent there too?

I had trouble getting Thunderbird to send through vzn even when I set it 
to the default, so I deleted all other SMTP servers including my Linode 
server.  When I try to send through VZN now, I get "An error occurred 
while sending mail. The mail server responded: Requested mail action not 
taken: mailbox unavailable. Please verify that your email address is 
correct in your account settings and try again"  In the few Verizon FIOS 
pages I could find that talk about sending mail, there's no mention of 
username (like 
https://www.verizon.com/support/consumer/email/settings/RK=2/RS=_dFiIjDkw9mkm81gv5I6vDDm9ww- 
)

So should I be sending mail through smtp.verizon.com or through my 
Linode server?

If I'm sending mail through my Linode server, then why would a block on 
my home IP address range matter when my MX records point to my  Linode 
server?

Does this have anything to do with IPv6?

Thanks.