Hi, it's only a small thing, but E.164 format does not include the +. If it includes the plus then it is E.123 format.
The Twilio page explaining E.164 formatting is wrong.
Care to elaborate? I've recently had to research E.164 and haven't come across this being mentioned. In fact I remember more sources claiming that the plus-sign is a required part of the format
The normal public telephone numbers we use are "International ITU-T E.164-number for geographic areas" and all E.164 numbers consist of the digit 0 to 9 only and no other characters. Spaces, symbols prefixes or suffixes do not form part of the number.
Section 12 explains that when a local code should be called in order to make an international call (e.g. dialling 00 from the UK or 011 from the USA) then E.123 suggests using the symbol + before the E.164 number. This symbol can be used when displaying the number to a human so the human can understand that they should replace the + with their local code to call internationally.
There's also a bit in section B.7 which describes CLIs and denotes that a CLI Should only be "the full international ITU-T E.164-number, i.e., country code (CC), national destination code (NDC) and subscriber number (SN). No other information, such as prefixes or symbols (e.g., "+"), should be included"