postfix-gmail problems: This mail is unauthenticated, which poses a security risk to the 550-5.7.26 sender

my flag

Can someone help, who had that problem too? Postfix and Dovecot is freshed installed and configurated for SSL but if i try to send an email to my gmail account i get that error msg.

Diagnostic-Code: smtp; 550-5.7.26 This mail is unauthenticated, which poses a
security risk to the 550-5.7.26 sender and Gmail users, and has been
blocked. The sender must 550-5.7.26 authenticate with at least one of SPF
or DKIM. For this message, 550-5.7.26 DKIM checks did not pass and SPF
check for [...] did not pass with ip:
[...]. The sender should visit 550-5.7.26 for 550 5.7.26
instructions on setting up authentication.
b11-20020adff24b000000b003063d97a9bbsi10649016wrp.1043 - gsmtp

I know, I know. Read the manual what I do, but its a bit hardcore because i dont understand all differences between spf, dkim and so on. Is that new from gmail, because one year ago it worked without that stuff. Maybe it was the TLS settings or whatever, because now i want to use only port 993 and 465 without the rest. Can someone give me some hints and help to find a readable solution for that? thx

update 1

I can send emails to other servers over only port 465 but cant recive an reply email from them to 993

2023-05-12T17:17:16.122149+02:00 web-p3 dovecot: imap([email protected])<18446><QSlzc4D71vIFtAyA>: Disconnected: Logged out in=392 out=3065 deleted=0 expunged=0 trashed=0 hdr_count=0 hdr_bytes=0 body_count=0 body_bytes=0
anx avatar
fr flag
Gmail used to not strictly enforce this rule and afaict they still only do when your published domain or hostname looks funny. But if you did see that message, that means you have to setup some form of authentication to push messages towards google. Which you should be doing anyway, if you are running a mail server, so not much changed.
trash2 avatar
my flag
@anx hi. i tried to send to gmail and thats the response. what you mean with funny hostnames? do you mean if my local server hostname is a1 and my domain ISP hostname is b2? so not equal over the same x.y domain? and what do you mean with setup authentification to push messages. thought if i set the ssl right, that would happens automaticly. sorry for that questions, but i am a noob at mailservers. and btw. from that article: "Important: Starting November 2022, new senders who send email to personal Gmail accounts must set up either SPF or DKIM. ". sry i saw that just right now =(
trash2 avatar
my flag
@anx thats so strange. i can send to other mailservers and it works (here it is the mailserver of my university). i recived an test email from [email protected]) so it seams that the port 465 works as he has to but i get that message if i try to send an reply to the [email protected]: **see update 1** i dont get any mail to my box =( seams dovecot 933 problems
fr flag

Your solution is to pretty much exactly what Google has recommended you do. Yes, that absolutely would involve understanding a number of supplementary (to SMTP itself) technologies.

It is hardcore, at least in the sense that in today's world you are not left with much choice other than setting up and complying with (at the very least) the demands of popular operators, or paying someone else to do so for you.

I would strongly discourage running your own mail server on the internet before investing substantial time into reading up on how the various protocols, mechanisms and ports work together. How you interact with your server via port 465 and 993 is generally quite separated from how mail exchanges interact with each other on port 25 and with each others names via DNS.


Post an answer

Most people don’t grasp that asking a lot of questions unlocks learning and improves interpersonal bonding. In Alison’s studies, for example, though people could accurately recall how many questions had been asked in their conversations, they didn’t intuit the link between questions and liking. Across four studies, in which participants were engaged in conversations themselves or read transcripts of others’ conversations, people tended not to realize that question asking would influence—or had influenced—the level of amity between the conversationalists.