Message filtering refers to the blocking of messages that are unwanted or illicit. Wireless Carriers may filter your message if it doesn't comply with regulations and/or their messaging policies.

Ensure that you only send messages to mobile users who have provided consent (opted-in) to receive messages from you.

Ensure that your messages clearly identify who is sending the message, and how to opt-out. If you are contacting the same recipients multiple times per month, you do not need to provide opt-out instructions in every message, but you must do it at least once per month.

The opt-out language you include in your messages must include a widely accepted keyword for opt-out. In the US and Canada this is typically STOP, e.g. "Reply STOP to unsubscribe." Using alternative phrases like "text 2 to opt out" is not compliant, and will result in filtering.

If you are sending messages to users repeatedly over a long period of time, you should check in with your recipients at least once every 18 months to ensure they still want to receive messages from you. The mobile number you are sending messages to may have changed owners, or the recipient may not remember giving consent to receive messages from you.

URL shortening: Do not send links that have been shortened using shared public URL shorteners, such as TinyUrl or free Bitly links. United States carrier policies discourage the use of shared public URL shorteners and state that your URL shortener should be both proprietary and properly branded. Other countries might not totally forbid using shared public URL shorteners, but it is not advisable. If you want to include shortened URLs in your messages, we recommend using a dedicated short domain.

If possible, when sending URLs/links in your messages, use domains that you control. Similar to the shortened URL guidance above, when sending links it is best to use a URL that is specific to your business. For example, if you control the domain mybusiness.net, you can be certain that only your business is using this domain, and nobody else could be sending URLs with that domain name that could link to objectionable content. Using URLs that may also be used by other services/individuals is permitted and is not guaranteed to result in filtering. However, it increases filtering risk, as another user of that same URL domain could send something spammy or objectionable and get that domain flagged by filtering systems. Obfuscated URLs are common in spoofing/phishing attempts, and will be filtered.

Don’t use emojis, or unnecessary special characters/capitalization, and watch your grammar and spelling. Typically, these messages are structured in a way to attempt to evade detection of unwanted messaging, and your messages will be filtered.

Do not send content that is illegal or is forbidden.