If the photo you try to upload into your forum message is too large for Attachment Manager to handle, you can adjust your smart phone to use less memory when taking the photo. Phones have been using more memory for each picture as the years go by. You can change a setting that will still give you excellent photos while reducing the storage needed and making them much easier to email, text and share on forums and social media. This will not change the size of your existing photos, you'll have to take new ones.
On an iPhone, follow the instructions on this link to make the change.
https://macpaw.com/how-to/reduce-photo-size-iphoneOn an Android phone with Google Camera, follow these instructions:
Open your Camera app
Click on the little gear icon to go to Settings
Click on the "More Settings" button
Scroll down to "Photo" and click on "Camera photo resolution" (See screenshot below)
Select "Medium Resolution" in the pop-up box
This will save you storage space on your phone, back-up space in the cloud and time and aggravation when sharing your photos online.
