Eddie asks whether the term "apostle" had a general sense, rather that the proposed, non-technical, semi-technical and technical senses. This seems to me to be a very good question, but one hard to answer. Thus far, I am happy with the view offered by Howard Marshall who states:
αποστολοσ is used throughout the NT as a Christian technical term for the authorised representatives of Christ or the churches who are engaged in particular tasks, usually connected with missionary work, including the establishment and supervision of churches, and who have delegated authority for the purpose.[Marshall, The Pastoral Epistles, pg. 118]
I am happy with the notion that the term apostle has its roots in the Hebrew concept of a Shaliach. Legally speaking, “The-one-whom-a-person-sends (shaliach) is like the sender” (m. Ber. 5:5). Thus, an apostle is a divine representative sent on specific task in the authority of the sender - [who has authority over the recipients?] The early apostles were commissioned by Jesus to go in his authority to perform certain tasks. This is where the term develops a distinctly Christian flavour in that they became the leaders of and in the community due to their distinctive relationship to their authoriser, i.e., Jesus himself. This gave them authority over the receivers. So long as the apostle is moving in the trajectory of the authoriser, he has authority.