Send emails over SMTP are not arriving to recipients

Dear specialist,

After setting up virtualmin over a clean ubuntu 18 server via digital ocean, i finally ( 2 days troubleshooting after sasl auth errors ) managed to sent mails with roundcube or over IMAP / SMTP via Wordpress.

I discovered that they are sent succesfully without errors. Via postman plugin in wordpress the log says :
postman log:
250 2.0.0 Ok: queued as 00FED1BDA04

xxxxx= hide details

My mail.log file :
Jun 8 20:04:16 customit postfix/smtpd[16928]: connect from[]
Jun 8 20:04:17 customit postfix/smtpd[16928]: 00FED1BDA04:[], sasl_method=PLAIN, sasl_username=xxxxxxx
Jun 8 20:04:17 customit postfix/cleanup[16930]: 00FED1BDA04:
Jun 8 20:04:17 customit postfix/qmgr[1224]: 00FED1BDA04:, size=3537, nrcpt=1 (queue active)
Jun 8 20:04:17 customit postfix/smtpd[16928]: disconnect from[] ehlo=2 starttls=1 auth=1 mail=1 rcpt=1 data=1 quit=1 commands=8
Jun 8 20:04:17 customit postfix/smtp[14704]: warning: dane configured with dnssec lookups disabled

However, I guess they haven’t left the queue cause I cant find the email anywhere? Not in spam or inbox. Tested with 3 different mail accounts : personal / hotmail / gmail.

Any ideas where the mails are? thanks!

Bet they’re in the que and probably being rejected by receiver. They are not “sent” until you see a “SENT” in mail.log.

Check webmin, servers, postfix, que. Bet there are emails there with error mesgs.

1 Like

Hi Scot,

You were right that all my mails got stuck in the /var/spool/postfix/deferred folder. With mailq command, found 36 mails. Did a flush to clean these up. Then run 2 tests :

  1. Send loopback email from -> : Works
  2. Send external email from -> : deferred again.

Seems like all external emails are refused by Hotmail, Gmail, Zoho mailserver.
There is 2 things which are constant in the /var/log/mail.log

  • I’m getting constant warnings: unknown[]: SASL LOGIN authentication failed: authentication failure. Are these brute force attackers? The ip-address change all the time.

  • Every time I send a mail, i find this at the end of the sending process in the log file : postfix/smtp[9798]: warning: dane configured with dnssec lookups disabled

Furthermore there is nothing else i can find. No errors or issues. Only issue is that emails are refused by recipients mailserver. My mailserver is also not on the blacklist. Zero blacklisted


Yes, those are people trying to login to send/recv email. Nothing can be done for that except strong passwords and some sort of firewall blocking for repeated abusers.

Go to and go through their email server tests. When I use, it shows there is a reverse dns problem. The mail server domain, IP, reverse IP(PTR), SPF, all must line up for gmail to accept mail from a domain. Others like hotmail or mircrosft are nearly impossible to send mail to from a new email server, so ignore them. And reverse dns is almost always handled by your hosting provider. You’ll have to get them to set it up.

Im afraid I have to let this email idea go. Too much headaches from this… I rent this droplet for my customers. Its a win-win. they have a fast and reliable website, maintained by me and ofc they pay me something for this. The only big pain, is that I have to outsource the emails. So the cost will be double : VPS + mail host. So there’s nothing to earn there.

You think using smtp relay like mailgun is an option to keep using the roundcube mailbox on my server?

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