Android
Send an MMS Message with Photos or Videos auf Android
MMS and SMS use the same messaging app, but the message type changes automatically the moment you attach a media file. A photo, video, voice clip, or contact card (vCard) all trigger this switch. Plain text alone always stays an SMS.
On a dual-SIM Android phone, MMS only works through the SIM that has an active mobile data plan assigned to it. If you pick the wrong SIM at the Choose a SIM card (Dual SIM) step, the message either fails silently or gets stuck as pending.
To send an MMS, tap Tap on Messages, then Choose a Conversation or tap on Start chat. Enter a Phone number or select a saved contact, then confirm the Choose a SIM card (Dual SIM) step if your phone has two SIMs. Type your Text message, tap Add, then Select the Type and pick the file you want to attach. Finish with Tap on Send.
If the message still wont go through after this, check that mobile data is enabled for the selected SIM, since MMS almost always needs a data connection even when WiFi is active. A weak signal or a data-saving mode can silently block MMS delivery even though the app shows no error.