I have installed the Synology Mailserver (not MailPlus) and would like to receive mails using IMAP.

I've created the following DNS records

sinnema.me      NS     ns1.isource.nl
sinnema.me      NS     ns2.isource.nl
sinnema.me      A
sinnema.me      MX(0)
ftp.sinnema.me  CNAME  sinnema.me
www.sinnema.me  CNAME  sinnema.me

I've forwarded and opened the following ports on my ISP's router (KPN):

SMTP           25
IMAP          143
SMTPS         465
??            587
IMAPS         993

Outlook somehow detects it needs mx3.isource.nl for sending and receiving emails. I've changed that to sinnema.synology.me which translates to

It doesn't make any difference if I use SSL/TLS or not, Outlook can't connect to the server.

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This is how it is configured in Plesk at the moment:

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  • Based on your comments below my answer I am not sure WHAT EXACTLY you are trying to setup. The most important question is if the mail client is on the Internet at large or on your local network where your synology lives. Then you likely need to look into the synology documentation about how to create email accounts there. Now, if you want to host your own incoming mail server, please reconsider, it is NOT EASY (I've been there and now I am cured): digitalocean.com/community/tutorials/….
    – Tomek
    Apr 6, 2019 at 15:41

2 Answers 2


IMAP server usually listens on ports 143 (plain text - unsafe & TLS) or 993 (SSL). You configured your client to connect to port 587 which is dedicated to email submission, not reception.

Additionally your MX record is incorrect. Right-hand-side should have hostname (Left-hand-side of A or AAAA record), not the plain IP address.

  • 587 is what Outlook prefilled it's not what I entered. So it should be 993? Can you elaborate on hostname? Previously it was like this sinnema.ch A which is an iSource IP address Apr 5, 2019 at 22:06
  • Ok, let's take another route. I really have no clue here what is wrong. I've been days at this now. What do I need to enter where to get this working. Requirements are: I would like to use IMAP. My domains are sinnema.ch, sinnema.me, tinygreenbits.nl and tinygreenbits.com. My router uses a DDNS called sinnema.synology.me which resolves to I've opened and forwarded the ports described (do I need more?). Who can tell me what to do next? Apr 5, 2019 at 22:15
  • In the mail server in the e-mail logbook mails are coming in so receiving is not the problem. Apr 5, 2019 at 22:53
  • I do get errors like: userid or password is wrong. What password do I need? is it the same password I use to log into my DSM? Apr 5, 2019 at 22:54

Your Modem and Mailserver settings seem to be configured correctly. Your Outlook configuration however is not at all what it should be:

  • Create a new account and enter the email paul@sinnema.me and check the 'I want to configure my email manually'.
  • Edit incoming Mail to sinnema.me and port 993 and set the encryption method to SSL
  • Edit Outgoing mail to sinnema.me and port 465 and set the encryption method to SSL
  • Press Next

Outlook will not always accept these settings on the first try so you may have to try a couple of times! If these settings do not work after a couple of tries there is something else wrong with your setup (try the IP address instead of sinnema.me)

  • Oh, and no need to forward port 587 to your server
    – Michel
    May 18, 2019 at 10:49

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