The Iranian MFA website proceeded their e-visa application page saying that all nationals except those from UK, USA could get a short tourist visa on arrival but that those nationals and others wanting some other type or duration of visa needed to apply via the e-visa. On checking a few days ago nationals from Pakistan, Afghanistan and some other countries had been added to the list of those that would not be offered VOA, I think Yemen, Somalia featured. But that is not the real point. The site simply states that it should either be done via e-visa or from one of their overseas embassies. Can you confirm it that is indeed the case?
At the moment you need to apply for your Iran visa authorization number through a travel agency to get a visa on arrival while in the past you could easily fly to Iran and at the airport get a 30 days on arrival visa. The visa on arrival is for 98 nationalities excluding USA, England, Canada, Colombia, Pakistan, Afghanistan, Iraq, Jordan, Bangladesh, and Somalia. If your nationality is among the countries authorized to get a 30-day on arrival visa, you can easily collect you visa against offering your passport, a passport-size photo and about $50-150 to the staff at the airport and by having your electronic Iran visa invitation letter already received from your Iranian travel agent. Fill in the visa form here , it takes about 10 days to get your electronic visa invitation letter (authorization letter). The payment for the visa invitation letter to the travel agency is different from the payment for the visa stamp. You may also apply for your visa beforehand from the embassy after getting the invitation letter from your chosen Iranian travel agency.