Alphanumeric sender ID in Germany and Austria: how your company name gets onto the recipient’s phone

An SMS that arrives from “+49 170 …” looks like a stranger. The same message from “MyShop” or “DrMuellerHH” is read, trusted and acted on. The difference is the alphanumeric sender ID: the name that replaces the phone number at the top of the message. In Germany and Austria it is simple to use, but there are rules about length, characters and behaviour that you should know before you choose a name. This article explains them and shows how the name is set when you send through TopSMS.

What an alphanumeric sender ID is

Every SMS carries an originating address. Normally that is a phone number in international format, up to 15 digits. The SMS standard (3GPP TS 23.040) also allows a second kind of originating address: a short text encoded in the 7-bit GSM alphabet. The phone displays that text instead of a number. Because of the way the field is packed, the text is limited to 11 characters; that limit is part of the standard and is the same on every network in the world.

Three practical consequences follow from this technical definition:

• Letters and digits only. Networks accept A–Z, a–z and 0–9 reliably. Spaces and punctuation are technically possible in some places but are dropped or rewritten by other networks, so treat them as unusable. Umlauts, ß and other accented letters are not safe either. A name must also contain at least one letter, otherwise it is interpreted as a (malformed) phone number.
• No reply is possible. The recipient’s phone has no number to answer to. The “reply” button is missing or greyed out, and nothing typed there reaches you. Any SMS sent under a name is therefore one-way communication.
• No contact matching. The phone cannot link the name to a saved contact and cannot call back. What the recipient sees is exactly the string you send, so the string itself has to be recognisable.

Germany and Austria: no registration required

German and Austrian mobile networks deliver alphanumeric sender names as they arrive from the gateway. There is no central register, no pre-approval by the operators and no per-name fee charged by the networks. You decide what the name is and it appears on the recipient’s phone with the first message. The same applies to most other European networks, although individual countries add their own conditions, for example for marketing messages, so check the destination before a campaign abroad.

“No registration” does not mean “anything goes”. Two things remain your responsibility:

• The name must not mislead. German competition law treats a message in which the identity of the sender is concealed or disguised as an unreasonable nuisance (§ 7 para. 2 no. 3 UWG). Pretending to be a bank, a parcel carrier or a public authority is not a branding choice but a legal problem, and gateways refuse such names.
• Filters exist. Operators and gateways watch for names that are commonly abused in phishing. A name that looks like a well-known brand you do not own, or a generic word such as “Info” combined with a link, has a higher chance of being blocked or of landing in the recipient’s spam folder. The TopSMS delivery report shows such cases with the reason rejected: the network refused the message because of the sender, the content or a block on the recipient’s side, not because the number was wrong.

Where the rules are different

If your customers are not only in Germany and Austria, check the destination before you build a sender name into your templates. The categories you will meet:

The rules outside Europe change often, so this table deliberately stays general. Our support will tell you the current situation for a specific country.

Choosing a good sender name

Eleven characters are not many. These guidelines come from what works in practice:

1. Use the name your customers already know. The company name as it appears on your website, invoices and shop sign, shortened only as far as necessary: “MuellerKFZ” beats “MKFZGmbH”. If your brand is a domain, the part before the dot is a natural choice.
2. Keep one name across all messages. Order confirmations, reminders and verification codes from the same sender build recognition. Phones group messages by sender, so the customer sees a single thread with your name.
3. Avoid spaces and special characters. “Dr Mueller” may arrive as “DrMueller” or “Dr?Mueller” depending on the network. Write it without the space from the start, and replace umlauts (Müller → Mueller or Muller).
4. Mixed case helps readability. “AutoHausKlein” is easier to read than “AUTOHAUSKLEIN”. Both are 13 characters, by the way, so this name would need shortening to “AutohKlein” or similar.
5. Do not use a name you have no right to. Not the name of a marketplace you sell on, not a brand you resell, not a generic term that suggests an official body.
6. Think about the reply problem. Because the recipient cannot answer, every marketing message needs another way to opt out: a short link, an e-mail address or a phone number. Transactional messages that invite an answer (“Reply YES to confirm”) do not work with an alphanumeric sender at all.

Setting the sender name with TopSMS

In TopSMS a sender name is an attribute of your account. You add it under Sender ID in the dashboard; once it is approved for your account you can use it in every message, and you can mark one name as the default. For German and Austrian recipients no operator registration follows. For Czech and Slovak networks we also submit the name to the operators, which is where the €20.58 fee and the waiting time come from.

When sending through the REST API, the name goes into the from field:

curl -X POST https://www.topsms.cz/api/sms/send \
  -H "Authorization: Bearer CLIENT_ID:SECRET" \
  -H "Content-Type: application/json" \
  -d '{"to": "+4915112345678", "text": "Your order #1024 has shipped.", "from": "MyShop"}'

A few details from the documentation worth knowing:

• from is optional. If you omit it, the account’s default sender is used; if no default is set, the message goes out as “TopSMS”.
• The API accepts only sender names approved for your account. An unknown name returns HTTP 403, so a typo in a template fails loudly instead of silently sending from the wrong name.
• If a name is approved for your account but the operators have not yet activated it (relevant for Czech and Slovak destinations), the message is sent as “TopSMS” and the response contains "senderFallback": true together with requestedFrom. After activation your name is used without any change in your code.
• In the dashboard and in campaigns you pick the sender from a list, so the same names are available there.

In the dashboard you can also send a test message to your own phone before you roll the name out. Seeing it on a real handset is the best check that the name reads well and is not rewritten by your own network.

Alphanumeric name or phone number?

A name is the right choice for almost all business messages: confirmations, reminders, codes and campaigns. A number is better only when you actually need replies, for example a dialogue with customers or a “reply STOP” opt-out. Many businesses combine both: notifications from the company name, and a normal mobile number or a contact page in the text for anything that needs an answer.