11 posts / 0 new
Last post
#1 Sat, 08/01/2009 - 15:46

SMTP issue


I have been browsing this forum in search of a solution or possibly a similar issue for several days already but to no avail. My problem is as follows:

I have installed Virtualmin using the install script on a fresh Centos 5.3 copy. I used to have some problems with DNS but those are solved already. Right now the only problem I have is that I cannot send mails using Outlook. I am using Postfix. I am 100% sure that my ISP is not blocking port 25 (I have contacted them + canyouseeme.org reports a service available on port 25). I have tried telnet localhost 25 from my server console and it works flawlessly, whereas telnet mydomain.com 25 from a remote PC times out. The funniest thing is that http://centralops.net/co/DomainDossier.aspx shows that there is SMTP service available on port 25. Outlook gives the following output: The connection to the server has failed. Account: 'mail.mydomain.com', Server: 'mail.mydomain.com', Protocol: SMTP, Port: 25, Secure(SSL): No, Socket Error: 10060, Error Number: 0x800CCC0E . Everything else: IMAP/POP3, sending mails through Usermin, receiving mails in outlook etc. works fine. If I run SMTP on any other port except 25 (ie 2525 or 26) it also runs smoothly. Any ideas will be appreciated.

Sat, 08/01/2009 - 16:09


Do you see any errors in /var/log/maillog when you try to connect? Also, are you sure that you've setup Outlook to authenticate outgoing requests? Some versions of it don't do that by default.

However, it might be helpful to see the domain name in question, as we can see if it looks correct from this end. You can always edit your post and mask it out once we get it working :-)


Sat, 08/01/2009 - 16:29 (Reply to #2)

Mail log doesn't show anything at all when I try to connect, it is just not being appended, as if Postfix cannot be reached from the outside. My domain name is bighost.lv and I am also ready to provide root password if needed.

Sat, 08/01/2009 - 16:31 (Reply to #3)

Okay, it shows up just fine from here, I see your SMTP service running.

So just to be clear -- do you see anything in mail.log that suggests that your IP address is hitting the server at all?

If not, something is definitely blocking your connection; do you have a PC at another location you can try? (ie, perhaps a friends house)

Also, in /etc/postfix/master.cf, you can enable SMTPS and Submission by uncommenting these lines near the top:

submission inet n       -       -       -       -       smtpd
  -o smtpd_tls_security_level=encrypt
  -o smtpd_sasl_auth_enable=yes
  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
  -o milter_macro_daemon_name=ORIGINATING
smtps     inet  n       -       -       -       -       smtpd
  -o smtpd_tls_wrappermode=yes
  -o smtpd_sasl_auth_enable=yes
  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
  -o milter_macro_daemon_name=ORIGINATING

By uncommenting the above (and restarting Postfix), you can connect using SSL on ports 465 or 587 -- perhaps you'd have better luck with one of those.


Sat, 08/01/2009 - 17:06 (Reply to #4)

No signs of my IP in the maillog. I will try both options: SSL and another remote PC. Thanks for timely response mate, I really appreciate it.

Sat, 08/01/2009 - 17:29 (Reply to #5)

I have just checked, SSL works like a charm. But port 25 mystery still remains unsolved :)

Sat, 08/01/2009 - 17:47 (Reply to #6)

Well, I'm a little suspicious of your ISP, many do in fact block outgoing SMTP to all but their own servers.

However, it could be any system between your desktop and your server.

Also, I've seen desktop security software (firewalls, anti-virus, etc) that blocked outgoing port 25 requests.

Just some thoughts!


Sun, 08/02/2009 - 02:09 (Reply to #7)

Well, frankly speaking now I also have a feeling my ISP is to blame. However, when I phoned them last time the support guy was very helpful and he checked the traffic both ways through port 25 and it was OK and definitely not blocked by them. Anyway, I will try to reach my server from another location today and if I fail I will phone my ISP again. Thanks for your assistance!

Wed, 08/05/2009 - 06:17

I have checked my SMTP server from at least 3 different PC and ISPs and it works perfectly! So probably the reason for my issue was my ISP or some software I run on my home PC. Thanks a million for your assistance!

Wed, 08/05/2009 - 09:37
ronald's picture

it probably doesn't resolve your issue per se but you do have some dns problems...


Wed, 08/05/2009 - 12:15

Ok, this one is solved: AVG Antivirus was blocking my SMTP connection. :)

2 ronald: Thanks for a nice link. I use temporary zoneedit.com DNS zone for testing purposes only. I will replace it with my own ns2.server before the server goes production.

Topic locked