email-server interview questions
Top email-server frequently asked interview questions
I understand you should not point a MX record at an IP address directly, but should instead point it to an A record, which, in turns, points to the IP address of your mail server.
But, in principle, why is this required?
Source: (StackOverflow)
I've used greylisting on my servers for many years, but I don't know how effective it is nowadays.
Is it still good for fighting spam in 2012?
Or is the typical spammer MTA capable of resending greylisted emails now?
Source: (StackOverflow)
I'm running Ubuntu Intrepid, and have been seeing the following my logs:
Aug 23 16:01:03 wp1 sm-mta[13700]: n7NFJIad013566: Warning: program /usr/sbin/sensible-mda unsafe: No such file or directory
Aug 23 16:01:03 wp1 sm-mta[13700]: n7NFJIad013566: SYSERR(root): Cannot exec /usr/sbin/sensible-mda: No such file or directory
Aug 23 16:01:03 wp1 sm-mta[13700]: n7NFJIad013566: Warning: program /usr/sbin/sensible-mda unsafe: No such file or directory
Aug 23 16:01:03 wp1 sm-mta[13700]: n7NFJIad013566: SYSERR(root): Cannot exec /usr/sbin/sensible-mda: No such file or directory
I have tons of these messages now, where I had none before. Looking it up, it appears Ubuntu has some special sendmail packages that might not have been installed when I installed sendmail.
Do I need "sensible-mda"? No one should be authenticating nor sending via the server - it's just a default local smtp host that's setup to allow for web forms to post to email, and for the system to send system logs, etc.
Why would these messages just start appearing?
Source: (StackOverflow)
I have around 5 websites hosted in a VPS server, and for some reason I bought another VPS server recently just to host the emails for those 5 websites. I would like to know the pros and cons of having a separate email server isolated from its web host.
I initially did it, to avoid having multiple software's in one server running. So, the likes of PostFix, Dovecot ... would not share resources and slow down mysqld, php-fpm ... but since I am a noob, I have no knowledge to back this assumption.
Source: (StackOverflow)
I need to send a large volume of emails, roughly 60.000 per week. At the moment we outsource this service to a third party, and we expect to double our volume within the next 6 months.
Since the service is starting to be too expensive, I was thinking about setting up our own MTA.
Our own SysAdmin told us it is not difficult at all to have our own MTA, but I'm afraid he might have oversimplified this.
Is it difficult to handle a MTA? Should I be afraid that my MTA will lose the company mails? Should I stay with a third party service?
p.s: The emails have been collected respecting the local legislation on privacy, so no spam.
Source: (StackOverflow)
I have postfix setup on my server so that I can send outgoing mail using the command-line:
mail -s "Subject" address@example.com
Is this using sendmail or postfix? Is "sendmail" just a software category or a distinct program? If something is "sendmail-ready" does that mean it will work with postfix?
Everything I've read online seems to use these two terms interchangeably.
Source: (StackOverflow)
I wanted to know the best way to make my mailserver send emails on behalf of my clients' domains, without being greylisted and also avoiding bounce problems.
I've been reading some other questions here, here and here but none explores all the possible solutions. Here are some possibilities that I would like to compare:
A.
HELO mymailserver.com
MAIL FROM<do-not-reply@myapp.com> # mymailserver.com same IP as myapp.com
DATA
From: <res@client.com>
Sender: <do-not-reply@myapp.com>
Question: This is what gmail does. It's the msg header "From:" that has a different domain, not the envelope sender.
emailclients will show "From:res@client.com via do-not-reply@myapp.com" or
"From:do-not-reply@myapp.com On Behalf Of res@client.com", which is not a problem for me.
Now, will this affect badly the reputation of my domain, the fact that the header "From:" has a different domain? (and if it's not Google who's doing it..)
B.
HELO mymailserver.com
MAIL FROM<do-not-reply@myapp.com>
DATA
From: <res@client.com>
# same as A, but no "Sender:"
It looks like Google once did this and called it a mistake
http://groups.google.com/group/Gmail-Help-Message-Delivery-en/browse_thread/thread/f651cb1db5d9dd23/3a8bcd0548487863?lnk=gst&q=%22on+behalf+of%22&pli=1
A bug removed the "Sender:" from their messages and the "via" didn't show up in the emailclient. (The RFC says that it MUST be present if it's not the same as the "From:")
C.
HELO mymailserver.com
MAIL FROM<res@client.com>
DATA
From: <res@client.com>
It's as if client.com were sending the message (the MAIL FROM is "spoofed" too). But if the client.com domain is well-known or has a SPF entry in its DNS, I would have to alter its DNS, allowing mymailserver.com to send message in their behalf.. (This is impossible for me because of the nb. of clients, and also some of my clients don't have control over their domains, i.e., are using @gmail.com themselves)
D.
HELO mymailserver.com
MAIL FROM<do-not-reply@myapp.com>
DATA
From: <do-not-reply@myapp.com>
Reply-to: <res@myclient.com>
Question: This is the simplest one, I would only add a "Reply-to:" header. Is this really taken into account ALL THE TIME by email clients? Can this be perceived as spoof too, adding different domains to the "Reply-to" header, and be a bad influence to my domain's reputation?
- The RFC only says that "if the Reply-To field exists, then the reply SHOULD go to the addresses indicated in that field and not to the address(es) indicated in the From field.".
- Only the "From:" header label would be "spoofed":
"From: myclient.com (via myapp.com) < do-not-reply@myapp.com> ".
Source: (StackOverflow)
How do I configure the Postfix mail submission agent to only allow emails to be sent out from a user on localhost , but allow the Postfix mail transfer agent to receive mail from anywhere?
Source: (StackOverflow)
My servers are currently on sendmail which is not very efficient. I'd like to migrate to PostFix.
I'm using Google Mail for Domain for handling incoming email so I need to setup PostFix to send emails only. What's the minimal PostFix configuration I must do to set up outgoing email delivery and prohibit receiving email? All localhost emails are trustable by default.
Source: (StackOverflow)
Is there something I can run from the command line that will let me query postfix (running locally)?
- if an address is in the virtual address file and,
- where the mail for that address is routed to.
Ex: If I have the email address of tim@domain.com. I want to ask postfix if that virtual alias exists and then see that it's mail get routed to tim11@mailserver.domain.com
Source: (StackOverflow)
I'll confess this is an area where I'll give it 10-20mb and toss out an "email is not intended for file transfer" whenever a user gripes about having to use FTP.
But a shiny new mail server deserves a rational approach... so what is a non-voodoo method for determining an appropriate limit for attachment size?
(Wavering on whether this is a wiki, or if there's a method that's Just That Good.)
I thought there would be some good guidelines independent of environment, but specifics were called for - so 50 mailboxes, exchange 2007, AD, hardware is TBD. Clients are a 2007/2003 mix, I figured I'd set sent/received to match, just to keep things simple.
Source: (StackOverflow)
I'm looking for an open source application that will archive my email. It might do this by logging in to my POP3 account on a regular basis and copying the emails across, or it might just read my Unix mbox/maildir file/directory directly on the mail server.
It must be open and it must run on Linux (or any open OS actually). Ideally, it would have a web interface, but this is not a major requirement.
MXsense (http://www.mxsense.com/mxsense.html) seems to be pretty-much what I want, except it's not open.
I have no requirement for MS Exchange support.
Any suggestions?
The rationale (maybe a bit silly) is that I run Linux exclusively and it's still doesn't have an email client that is anywhere close to MS Outlook in terms of awesomeness, so I find myself switching between mail clients often. I would feel better about this if I had an archive of my emails, so it wouldn't matter which mail client I was using this month.
Source: (StackOverflow)
When setting up a web/mail server on a single server or VPS with one IP address almost every guide online follows the same structure for DNS:
example.com. IN A 192.0.2.0
hostname.example.com. IN A 192.0.2.0
mail.example.com. IN A 192.0.2.0
example.com. IN MX 10 mail.example.com.
0.2.0.192.in-addr.arpa. IN PTR hostname.example.com
I used this several times and it has always worked for me. But I was wondering if there's a reason why the mail server points to a different name? Would it be possible to point the MX record to the hostname and simply use hostname.example.com for SMTP and POP3?
Source: (StackOverflow)
I'm going to get a Windows 2008 dedicated server sometime soon. I'm going to have my website hosted on it, so, I also want to run a mail server on the same machine to receive any mail sent to the website (I use the SMTP Server in IIS for sending mail, but this about receiving not sending)
Does Windows 2008 have a built-in POP3 OR IMAP server? If so, can it be accessed through a webmail interface? I mean does it also have a webmail interface similar to OWA for example? If not, do you have suggestions for a good mail server with a webmail interface, preferably free or open source? MS Exchange is above my budget and my needs are so simple anyway. I heard good things about hMailServer but I checked and it doesn't have a webmail interface.
I know I can outsource this to a third party for a little monthly fee, but I prefer to host my own server.
Thanks for any suggestions
Source: (StackOverflow)
When I try to send an email on my postfix server to an address on the same domain (for example, if the server hostname is mail.example.com and I try to send an email to test@example.com), I get the following error in the log and the email is not delivered: Recipient address rejected: User unknown in local recipient table. If I send to an address on another domain, I don't have any problems. Here is my /etc/postfix/main.cf file:
smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no
# appending .domain is the MUA's job.
append_dot_mydomain = no
# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h
readme_directory = no
# TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.
myhostname = mail.example.com
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
#myorigin = /etc/mailname
myorigin = $mydomain
mydestination = $mydomain, localhost.$mydomain, localhost
relayhost =
#fake IP address
mynetworks = 127.0.0.0/8 100.837.191.223
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
Source: (StackOverflow)