Cannot sync... 500 error #654

kicker334 · 2025-08-16T02:02:58Z

kicker334
Aug 16, 2025

Ever since the update, I can't sync anymore. I get a 500 error.

I can take the URL I'm using and put it in a browser and download the ICS just fine. So I know the link works. I also haven't changed the link in years.

It does the same thing on mine and my wife's phones.

HTTP 500

java.io.IOException: HTTP 500
at at.bitfire.icsdroid.CalendarFetcher.fetchNetwork$icsx5_88_2_3_1_gplayRelease(SourceFile:180)
at at.bitfire.icsdroid.CalendarFetcher$fetchNetwork$1.invokeSuspend(Unknown Source:11)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(SourceFile:33)
at kotlinx.coroutines.DispatchedTask.run(SourceFile:100)
at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(SourceFile:586)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(SourceFile:829)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(SourceFile:717)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(SourceFile:704)

Answered by ArnyminerZ

Aug 22, 2025

We are still going to support custom agents, followup in #663. But it looks like that as of 2025/08/22, Microsoft has reverted some changes, and this is working fine.

View full answer

casta · 2025-08-17T18:09:11Z

casta
Aug 17, 2025

I get this one with Office365 ics files since yesterday too. Other ics are perfectly fine.

It seems that Microsoft is doing something weird with UserAgent:

getting the file with firefox or chrome/vivaldi => OK
getting the file with thunderbird => KO
getting the file with icsx5 => KO
getting the file with curl => KO
getting the file with curl by faking firefox UserAgent (-H 'User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:141.0) Gecko/20100101 Firefox/141.0') => OK

In the KO case, Office365 issues a redirect to a 500 error page:

$ curl 'https://outlook.office365.com/owa/calendar/<redacted>/<redacted>/<redacted>/reachcalendar.ics'  
<html><head><title>Object moved</title></head><body>
<h2>Object moved to <a href="/owa/auth/errorfe.aspx?httpCode=500&amp;msg=3673577647&amp;owaError=Microsoft.Exchange.Clients.Owa2.Server.Core.OwaBasicUnsupportedException&amp;owaVer=15.20.9052.11&amp;be=VI1PR04MB9858&amp;ts=133999274192922857&amp;fe=VI1PR0202CA0025&amp;reqid=&amp;creqid=&amp;cid=&amp;hmac=oBKsn7P3bAWf9D9ZmqCNoRlZCw3x87qMnle5O2Lw5fk.">here</a>.</h2>
</body></html>

So either it’s a definitive change, and this should be sorted out (fake user agent?), either Microsoft has released some bogus change that will be fixed, and… just wait?

4 replies

fibsifan Aug 18, 2025

Maybe they "just" changed some global policies and there would be a workaround if one can convince one's Organization Admin to allowlist the ICSx5 User Agent?

https://support.calendar.com/hc/en-us/articles/4407450262669-Troubleshooting-your-Office-365-integration-Access-Policy

I am not sure, whether not being on the allowlist results in a 500 error.

kicker334 Aug 19, 2025
Author

I know my org won't change policy for something like this. :(

casta Aug 19, 2025

I don’t think so: this URL is a public calendar sharing URL, not EWS endpoint. Those policies relates only to EWS access.

curledUpSheep Aug 21, 2025

This really seems like a bug on Microsoft side that should be fixed.

Tested with Postman:

Standard Postman UserAgent header: 500 Internal Server Error, page contains the text "Outlook is not supported on this browser. Not all web browsers support Outlook on the web." (as if we're trying to open the Outlook web UI instead of just getting ICS data)
Fake Firefox UserAgent header: works normally
No UserAgent header at all: Postman complains that the maximum number of redirects has been exceeded, indicating that the request is probably stuck in a redirect loop

kicker334 · 2025-08-17T18:18:59Z

kicker334
Aug 17, 2025
Author

Microsoft doing Microsoft things it sounds like then.

0 replies

kicker334 · 2025-08-19T01:44:16Z

kicker334
Aug 19, 2025
Author

I don't know enough about coding to figure out what even to request as a change. But is that something the developer could work on if it is a 365 URL?

1 reply

sunkup Aug 19, 2025
Maintainer

We might. See #655

shemminga · 2025-08-20T00:43:19Z

shemminga
Aug 20, 2025

I'm encountering the same issue, so I did a bit of testing and they seem to check on a few very specific things.

The current UA for me: ICSx5/2.3.1 (ical4j/3.2.19 okhttp/5.1.0 Android/16)

Working UA: ICSx5/2.3.1 (ical4j/3.2.19 okhttp/5.1.0 Linux Android 16) like Chrome/30

The differences are:

Linux needs to be inside the parenthesis
Android 16 only works without the /
like is not needed
Chrome/30 and higher numbers work; numbers lower don't

From the linked discussion, I understand that there's some worry about lying in the UA string. I think these changes are fair: each of them is true and has a precedent in the UA strings of major browsers. Chrome's UA for example mentions that it's "(KHTML, like Gecko)". Edge and Opera just put Chrome/xxx strings in there. See https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/User-Agent for examples.

Changing the UA string like this might be an easy solution to fix the big Outlook/Exchange ecosystem, without building full UA customization.

2 replies

sunkup Aug 20, 2025
Maintainer

Thanks for sharing! That is helpful to know indeed 👍

ArnyminerZ Aug 20, 2025
Maintainer

After an internal talk, this will be implemented in #655

sanderlv · 2025-08-20T17:32:59Z

sanderlv
Aug 20, 2025

Same here, so ended up here. since a day of 5 indeed.

Example link:
https://outlook.office365.com/owa/calendar/[email protected]/690f822484734496b8680fb573a91c3811678143038089895600/S-1-8-254772858-1127038197-1900326193-2373556498/reachcalendar.ics

0 replies

kicker334 · 2025-08-22T02:06:02Z

kicker334
Aug 22, 2025
Author

Suddenly today it started working? I'm guessing a fix was not made on this side, right? Maybe Microsoft fixed their end?

8 replies

shemminga Aug 22, 2025

Yes, it works for me too. Looks like Microsoft fixed it on their end.

sanderlv Aug 22, 2025

Yes fixed

Grimmwicht Aug 22, 2025

Still not working for me, neither on phone nor on Thunderbird. Same as in first post: HTTP error 500, but could download the .ics directly.

One of the dysfunctional links:
/owa/auth/errorfe.aspx?httpCode=500&msg=3673577647&owaError=Microsoft.Exchange.Clients.Owa2.Server.Core.OwaBasicUnsupportedException&owaVer=15.20.9052.17&be=FR1PPFF3DE105D0&ts=134003632039228447&fe=FR2P281CA0169&reqid=&creqid=&cid=&hmac=uj7PvepFvNjtSKWOOZg0FEvMm-fwKZQBTh818AiUdFs.

kicker334 Aug 22, 2025
Author

Microsoft tends to roll things out. So I am guessing if it is a fix it may take a bit to roll out to everyone. But I appreciate the developers wanting to get something usable regardless.

graue70 Aug 29, 2025

In that case, I'm still waiting for the roll out to reach me. As of now, it is still broken. The last successful sync was ten days ago.

ArnyminerZ · 2025-08-22T12:59:19Z

ArnyminerZ
Aug 22, 2025
Maintainer

We are still going to support custom agents, followup in #663. But it looks like that as of 2025/08/22, Microsoft has reverted some changes, and this is working fine.

5 replies

sunkup Aug 25, 2025
Maintainer

guess they might have experienced issues with other clients as well ...

ArnyminerZ Aug 25, 2025
Maintainer

Yup, it must be the case

sunkup Sep 3, 2025
Maintainer

New version is on its way. Expect it to take some time to arrive in the Play store and F-Droid. If you don't want to wait you can download it from the release page: https://github.com/bitfireAT/icsx5/releases/tag/v2.4.0

sunkup Sep 3, 2025
Maintainer

With the new version installed you can set the user agent string per subscription. Either when adding a new subscription or simply by editing the existing one. See also: #681 (comment)

rzo1 Sep 4, 2025

Works fine with this UA ICSx5/2.3.1 (ical4j/3.2.19 okhttp/5.1.0 Linux Android 16) like Chrome/30. Thanks!

sjonez · 2025-09-02T15:50:04Z

sjonez
Sep 2, 2025

This has started happening to me this morning, from testing anything but a browser user-agent now redirects the request to /owa/auth/errorfe.aspx?httpCode=500&msg=3673577647&owaError=Microsoft.Exchange.Clients.Owa2.Server.Core.OwaBasicUnsupportedException

0 replies

FelixBuehler · 2025-09-11T10:54:13Z

FelixBuehler
Sep 11, 2025

So does the new update work for you guys? Since the initial change, I can't get my Office ics calendar to work. If I don't use a custom user agent, I get a HTTP 500 error, when I use a custom one I get "Couldn't parse iCalendar".
But when I download the file via my computer and import it into icsx5, everythin works fine. I'm confused.

4 replies

sjonez Sep 11, 2025

Setting the custom user agent stopped the 500 for me but I now get hit by a timeout in the new version because it takes >10s to generate my ICS. I raised #683 which is fixed in the next release

sunkup Sep 11, 2025
Maintainer

Should be fixed in 2.4.1 - https://github.com/bitfireAT/icsx5/releases/tag/v2.4.1

Will arrive in play store when google has verified it and in F-Droid when they have built it.

sjonez Sep 11, 2025

Yes, that's fixed it. All syncing fine now 💯

sunkup Sep 11, 2025
Maintainer

@FelixBuehler If you share the ICS file or the subscription link with us we can take a look at the "Couldn't parse iCalendar" error. Feel free to send it to [email protected] and mention this discussion in case you don't want to share it here.

Uh oh!

Cannot sync... 500 error #654

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Replies: 9 comments · 24 replies

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kicker334 Aug 19, 2025 Author

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kicker334 Aug 17, 2025 Author

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kicker334 Aug 19, 2025 Author

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sunkup Aug 19, 2025 Maintainer

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sunkup Aug 20, 2025 Maintainer

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ArnyminerZ Aug 20, 2025 Maintainer

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kicker334 Aug 22, 2025 Author

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kicker334 Aug 22, 2025 Author

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ArnyminerZ Aug 22, 2025 Maintainer

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sunkup Aug 25, 2025 Maintainer

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ArnyminerZ Aug 25, 2025 Maintainer

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sunkup Sep 3, 2025 Maintainer

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sunkup Sep 3, 2025 Maintainer

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Replies: 9 comments 24 replies

kicker334 Aug 19, 2025
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kicker334
Aug 17, 2025
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kicker334
Aug 19, 2025
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sunkup Aug 19, 2025
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ArnyminerZ Aug 20, 2025
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kicker334
Aug 22, 2025
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kicker334 Aug 22, 2025
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sunkup Aug 25, 2025
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