iOS: Carddav account verification failed

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iOS: Carddav account verification failed

Operating system
  1. Windows
Mobile operating system
  1. Android

I have a Synology DS1019+, accessible over the internet on its own domain; custom DSM port and a reverse proxy from 443 to the custom port. Synology Contacts is installed and I've managed to connect to it on my Android device without any issues.

However, if I try to add a new CardDAV server on my iPhone (iOS 14.1), I keep getting an error message saying " Carddav account verification failed". If I still save the configuration, another error message almost immediately pops up saying the password is incorrect. Now, the password is correct, of that I'm sure. Moreover, I've successfully done the same for CalDAV on the same server, with the same credentials.

Can anyone help me figure out what the issue is, please?

Show the UI of the configuration. It could be that you are missing a "/" (slash) character after your username inside the "server path" element. It is not there by default. This is usually the problem with CalDAV so it might be a problem here as well.
This is what I have
At some point I even tried the second URL that Synology Contacts has for CardDAV Clients.


Not really, no.

I don't know if that's a concern, but I've got 2-factor authentication enabled - but that doesn't seem to affect the connection on my Android device. Moreover, I even tried disabling it at some point and iOS showed the same error.
Last edited:
I don't know if Synology Contacts is configured on a specific port. I'll look into that.

But in the meantime, I did a test and tried to connect Thunderbird on my Windows laptop to the CardDAV Client URL and it didn't accept the password! This is the very same password that I use to log in to DSM and from then open Synology Contacts.


<d:propfind xmlns:d="DAV:"><d:prop><d:current-user-principal /></d:prop></d:propfind>

Access to the requested resource forbidden.

Could it be that I have 2FA enabled? Is Synology Contacts expecting a sort of app-passwords like Google used to do in the beginning?

EDIT: Figured it out! I'm using a custom DSM port and for some reason the Android client (DAVx5) is capable of "guessing" the correct number just from the URL, but the $1000 iPhone is not. Put the custom DSM port in the URL on the iPhone config and Bob's your uncle!
There are two 'contacts' packages: CardDAV Server and Synology Contacts. OK so we all know this.

  • CardDAV Server:
    • It has its own ports for HTTP and HTTPS
    • Control Panel -> Application Portal -> Reverse Proxy
      • direct domain and specify HTTP and HTTPS ports to the CardDAV Server ports.
  • Synology Contacts:
    • Uses the DSM portal approach by being launched from within the portal, or
    • Control Panel -> Application Portal
      • direct alias but using the DSM's web ports
      • direct domain using standard HTTP/HTTPS ports
      • its own ports for HTTP and HTTPS

So assuming it is Synology Contacts and Application Portal with a direct domain '' then this just worked for me on an account with 2FA...
  • Server:
  • Username: <my user>
  • Password: <my password>
Is it normal that I'm not able to edit or delete contacts from my iPhone to Synology Contacts? I can do it just fine on Android.
EDIT: Figured it out! I'm using a custom DSM port and for some reason the Android client (DAVx5) is capable of "guessing" the correct number just from the URL, but the $1000 iPhone is not. Put the custom DSM port in the URL on the iPhone config and Bob's your uncle!

Ok. Good to know that the new Synology Contact packages does CardDAV over the DSM port instead of 443 (why on earth............).....
I also ran into this issue and found this. Thanks for finding the solution.

I too was very confused, in fact I had to let the setup fail once so that I have the chance to provide specific port in iOS. Tried DSM port for once actually but it didn't work because I forgot to open the port in firewall (typical error).

DSM knowledge base has instruction about this but they should emphasize the DSM port, also it's in conflict of the claimed CardDAV port provided here:

DiskStation Manager - Knowledge Base | Synology Inc.

This is quite broken, luckily it still kind of works. I reported a ticket at Syno, hope they'll fix it if more people report the issue.
I too am having an issue with syncing with Synology Contacts. I am using a URL with, as that's what I copied from DSM. I first get a message saying I can't connect with SSL, then I see it fails altogether.

I also tried with the slash at the end of the URL - no luck.

Should you be able to sync contacts with a URL? Any other thoughts?!



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