Central Email Gateway TOC Cannot send this item

Question

My client has been using the email gateway for some years now. 
 About 6 months ago my client reported that emails would not send, they received a message saying Cannot send this item. After investigating I found it related to long URL's, once an email chain gets so long the links block the reply emails being sent We use TOC via the email gateway, this is the cause of the issue as it rewrites the URL every time an email is sent even though it rewrote them previously. MS released a fix for this in April: https://www.bleepingcomputer.com/news/microsoft/microsoft-fixes-outlook-cannot-send-this-item-email-bug/ This didn't resolve the issue my client is having, the fix may have been for 365 TOC. I have logged cases with support but not got anywhere, has anyone else seen this problem?

Tom Foucha · Accepted Answer

We have an upcoming code release that helps reduce the size of the URL when rewritten. The character limit is known issue. We expect the fix to be available in the next 60-90 days, if we can deliver it sooner we will. As I get more details I will update this thread.

Tom Foucha · Answer

A partial fix for URL's rewritten that traverse from one Sophos Customer in a region to another Sophos customer in another region has been implemented. The complete fix for all rewritten URL's is still under development/testing and expected by end of year.

emmosophos · Answer

Hello there, 
 Thank you for contacting the Sophos Community. 
 May know the Case ID(s) you have logged, to see what has been done. 
 Regards,

emmosophos · Answer

Hello there, 
 I tried searching for your Case ID, but I couldn't find it under the email you used to register to the community. 
 I did found 3 cases related to this, however, they were about users having a mail signature, that was causing the re-written, it was suggested to add this signature to the Central Email > Settings > URL allow list. 
 I am not sure if this would be also your case. 
 Regards,

Tom Foucha · Answer

After Wednesday it will be deployed for all customers. Today it was deployed for EU-West region. Our deployment continues. Once deployed you can test by sending an email with a URL containing more than 2048 characters. It would automatically decrease the size of that URL to below that limit.

Tom Foucha · Answer

We further rolled out to one region this morning a fix that I've seen take a 2156 character URL down to 383 characters after the rewrite by our Time of Click protection (Toc). We will be rolling this out globally over the next week. 
 I'm excited to put this to rest!

Tom Foucha · Answer

As mentioned above and posted in announcements this fix has been deployed globally.

Øivind Hagenlund · Answer

The issue seems to be way more prevalent on the current Office channel, so we're switching to the semi-annual enterprise channel, and that seems to help a lot, but doesn't completely eliminate the issue. This means we've also had to whitelist *.safelinks.protection.outlook.com in the Sophos Central portal. So we're not actually using Sophos Time of Click for email protection on sites that have gone through Exchange Online, which defeats the purpose of using Sophos ToC in the first place. 
 I wish Sophos could just shorten their ToC links, but for some reason they just don't want to do that, and instead prefer that we stop using their product.

Central Email Gateway TOC Cannot send this item

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