Well, Internet routing issues, certificate issues, bad wifi connections, bad 3G/4G connections or pretty much anything that is part of the network connection between the mobile device and the web server that provides the images. 

Hi!
I run Mercury 4.80 on our home server and we've long had the problem that some e-mails timeout when we try to view them on our i-devices (iPhone, iPad). I have tried to find some common criteria for these e-mails, and today I found what I think is the reason. All of these e-mails contain image links (IMG src=) to external web addresses using HTTPS. If an e-mail only contains image links to external web addresses using HTTP, there is no problem. Of course, I can't be 100% sure this is the cause, but after going through dozens of e-mails this was the only thing that was consistent when we got the timeout.

Snippet from source of e-mail that times out, so you see what I mean:
"<img alt="Ett extra helg-erbjudande" src="https://dh1u9ipksig21.cloudfront.net/Global/Mejl/Veckomejl/2016/30/vara1_SH_v30_16.jpg" style="-ms-interpolation-mode: bicubic; height: auto; line-height: 100%; outline: none; text-decoration: none; max-width: 300px; max-height: 180px; border: 0;" /> 

Can anybody tell me why this is happening and what I could do to fix it?

In a case like this the entire message, including the link, is transferred to the client from Mercury. The client will then try to connect to the linked resource to display it. This could fail because of for instance bad connection to the web server, some firewall filter or, for HTTPS, a problem with the server certificate. If this is specific to the email client used in the i-device there may be some dedicated forum for that app that can provide further help.

OK I'll try to explain in more detail. When an email client connects to Mercury it will download the message body, which could be in plain text, in HTML, or both. When download is complete the client will attempt to display the message. For HTML coded message parts an HTML renderer will interpret tags, style sheets and all other content. If there are images to display they can either be included in the email message or linked from a web server somewhere on the Internet. The image tag that you quoted contained such a link. The mail server (Mercury or any other brand of server) is not at all involved in getting linked resources, the clients sends the request directly to the web server specified in the link.

That said there could be something else in the message that could cause an issue in Mercury. If you zip the CNM file and post it here we can check if something seems suspicious. 

I've uploaded the CNM file here:

https://webclient.rushfiles.one/publiclink.aspx?saf2=mObTH199xcjz6ZpPdQ9oXvLiJKDM8f 


/Anders

I checked the MIME structure and tested it with my normal email client, and so far everything looks normal. Tomorow I'll see if I can get one of our Iphone users to test it as well.

Thanks

One of our Iphone users helped testing it now, and the message displayed instantly in her email client.

Do you by any chance have some kind of web content filter in your firewall or Internet router? 

No filter, and as I said earlier the same message opens fine from another (external) mail server. Any other ideas what could be causing it?