CentOS: Postfix not forwarding emails

Hi All,

I've been running a VPS server for around 3 years.  I use postfix to forward email onto my customers.  This has worked very well.

Today however I noticed emails are not being forwarded.

I've restarted the server, but that hasn't helped.

An SMTP test on mxtoolbox.com shows everything is working and port 25 is open.

Any ideas what I can look at?  I have root SSH access to can run any tests etc...

Many thanks
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Nick UpsonPrincipal Operations EngineerCommented:
I'd start by looking at /var/log/maillog assuming default location
detox1978Author Commented:
Any ideas?

Mar  2 03:42:03 www postfix/error[8893]: B7D14A2AC7: to=<relayaddress@example.com>, orig_to=<orginal@example.co.uk>, relay=none, delay=92734, delays=92733/0.86/0/0.01, dsn=4.4.2, status=deferred (delivery temporarily suspended: lost connection with mx-eu.mail.am0.yahoodns.net[] while sending RCPT TO)
detox1978Author Commented:
Looks like yahoo are rejecting my emails, as people are spamming my catch all email addresses.

Mar  2 03:42:03 www postfix/smtp[8834]: 2102DA2FA6: to=<recipientemail@example.com>, orig_to=<spam@address.com>, relay=mx-eu.mail.am0.yahoodns.net[]:25, delay=63404, delays=63403/0.05/0.41/0.09, dsn=4.7.1, status=deferred (host mx-eu.mail.am0.yahoodns.net[] said: 421 4.7.1 [TS03] All messages from [My server IP] will be permanently deferred; Retrying will NOT succeed. See http://postmaster.yahoo.com/421-ts03.html (in reply to MAIL FROM command))

Any ideas?
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Nick UpsonPrincipal Operations EngineerCommented:
I agree
detox1978Author Commented:
Is there anything i can install via YUM to resolve these issues?  maybe something that ill stop excessive connections from one IP
No, Basically you need to setup your mail server with server-key, SPF, DKIM etc.. so yahoo treats your mails are genuine mails and accept those. Please find the below reference for yahoo policies.



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or send your email through another host, or ask yahoo to whitelist you if you have a legitimate reason to send that many email.

spf might be a good candidate in order to explain why you got blacklisted : if one of the addresses you send addresses from does not belong to you and the spf record does not include your external IP as an allowed forwarder

correcting such stuff will not deblacklist you at once. yahoo probably will blacklist you for a day to a week

in the mean time, you should stop sending mail because hammering on their door will probably increase the blacklisting period
beware : as long as you keep sending spam, having proper spf records and dkim and the likes will hardly make a difference

actually most filters will only care about wrong records
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