[OPLINTECH] Something to keep in mind about various email providers

[Bob Neeper]

FWIW

We have been running eTicket on an internal server for quite a while.
Even though a 10.x.x.x it was able to send emails to our OPLIN accounts.

Now we have 1and1 service, which ignores the emails. gmail accepts them.

A log (for eTicket messages) on the server shows:

2015-05-27T14:06:54.092279-04:00 StaffWeb postfix/smtp[23851]: C40684393F: 
to=<bob at yourcl.org>, relay=mx01.1and1.com
[74.208.5.21]:25, delay=0.29, delays=0/0/0.28/0, dsn=4.0.0, status=deferred 
(host mx01.1and1.com[74.208.5.21] refused to talk to
me: 554-perfora.net (mxeueus004) Nemesis ESMTP Service not available 554-No SMTP 
service 554 invalid DNS PTR resource record,
IP=66.213.124.227)

2015-05-27T14:06:55.242391-04:00 StaffWeb postfix/smtp[23850]: C27AE43942: 
to=<neeperro at gmail.com>, relay=gmail-smtp-
in.l.google.com[74.125.201.27]:25, delay=1.4, delays=0.01/0/0.48/0.95, 
dsn=2.0.0, status=sent (250 2.0.0 OK 1432750004
th17si142130icb.46 - gsmtp)

1and1 error message information shows:

550 No SMTP Service
The IP Address of the email Server you use is not allocated a domain name in the 
domain name service (DNS).
Please contact your Administrator to add the domain name to the domain name 
service.

550 Bad DNS PTR resource record
The e-mail server you are using employs is using a dynamic IP address.
To deliver your e-mail please use the Smarthost of your provider to deliver 
e-mails.


So it seems (I think)
Many email servers will check for PTR records to ensure mail is not spoofed. 
PTR's are basically reverse DNS.
If they receive an email from w.x.y.z from somebody at foo.com, they do a look up 
on w.x.y.z to ensure it is really foo.com.
If not, they ignore the email.

And our internal only server doesn't meet requirement for 1and1, while google 
doesn't care.

Bob

-- 
R. W. (Bob) Neeper
(Retired Toledo Scale Engineer & Computer Guy)

Volunteering at:
Community Library
44 Burrer Dr.
Sunbury, Oh 43074
Tel:  (740)-965-3901