A recipient has to receive it for the act to be complete. In every case of abusive tweets yet prosecuted, the tweet was received by the complainant in their own account.
I bow to your superior knowledge, John.
I am sure the CPS will welcome your expertise, and will hasten to correct their guidance in respect of the act:
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Threatening letters or other articles - Section 1 Malicious Communications Act, 1988
"The Malicious Communications Act 1988 section 1, see Stones 8.20830, deals with the sending to another of any article which is indecent or grossly offensive, or which conveys a threat, or which is false, provided there is an intent to cause distress or anxiety to the recipient. The offence covers letters, writing of all descriptions, electronic communications, photographs and other images in a material form, tape recordings, films and video recordings. Poison-pen letters are usually covered.
Particularly serious examples may justify a more serious charge, e.g. threats to kill.
The offence is one of sending, delivering or transmitting, so there is no requirement for the article to reach the intended recipient. The terms of section 1 were considered in Connolly v DPP [2007] 2 All ER 1012, and "indecent or grossly offensive" were said to be ordinary English words. The fact that there was a political or educational motive behind the accused sending graphic photographs of aborted foetuses did not help her, and her argument that her behaviour was protected by Articles 9 and 10 ECHR (freedom of religion and speech) did not succeed, because the restrictions on those rights were justified under Articles 9(2) and 10(2).
A person guilty of an offence under section 127 CA 2003 shall be liable, on summary conviction, to imprisonment for a term not exceeding six months or to a fine or to both.