When the PredictMail via Iridium setting is enabled on the Satellite -> Iridium GO! or Iridium GO! exec Settings pages, PredictMail image resampling is enforced on the DataHub. The DataHub will resize images to reduce them before images are sent.
Outbound resampling greatly reduces the size of an Email with attached images. Size reduction will vary based on the type of image, but in general, you can expect it to be about 10x smaller than what is sent from your email App.
Resampling outbound Emails can take some time. Several large images (3-4Mb+) may take an hour or more. This is done in batch mode in the background without impacting airtime usage. The email will not be sent until resizing is complete.
You can see this setting enabled on the Services->PredictMail->Filtering tab:
How to bypass PredictMail image resampling
Image resampling can be bypassed for a particular email by adding the modifier "+noresample" to the email address. As example:
becomes:
The following modifiers are currently supported:
+BypassSize - Bypass the outbound max size filter
+NoResample - Don't resample images and bypass the outbound max size filter
Here is an example of a 4.6mb image (6.3mb when MIME encoded for email) being sent with +noresample to bypass image resampling:
Whether that will upload successfully depends on your Internet connection's speed and quality. These would send quite quickly over high-speed Wi-Fi, Starlink or 4/5G Cellular when coastal. Half a megabyte may work successfully with a GO exec on a well-positioned external antenna offshore.
For example, a 600Kb image, when MIME encoded for email, could be 1000Kb in size. With a GO exec having a full 5 bars of coverage at a sustained 22Kbit/s upload speed, it would take around 6 minutes to upload the 600Kb image email. Given your particular boat and antenna setup, testing it to see your results is best.
To manage the input size, it is recommended that you crop and resize the image first using a photo App before bypassing resampling when you send it.