My iPhone 6 sends and receives texts just fine, but when I try to send a photo, I get an error?

[iMore Question]

my iPhone 6 sends and receives texts just fine, but when I try to send a photo, I get the error:

my iPhone 6 sends and receives texts just fine, but when I try to send a photo, it won't send. iMessage is enabled, and I've reset it several times.

 

[Branta]

Re: my iPhone 6 sends and receives texts just fine, but when I try to send a photo, I get the error:

Not enough information yet to identify the problem. Questions...

Which cellular network?
Is the recipient on the same network? Same country?
Is the recipient also using iPhone? Some other smartphone? Basic cellphone?
Is the phone working OK for other data like web sites?
Sending photos by iMessage (data), or by MMS (old style like SMS)?
In iMessage can you send simple text to the recipient? Do the sent messages show in blue (sent via iMessage data) or green (sent by SMS)?
If sending by MMS, how big (kilobytes / megabytes?) is the photo?