He is being asked to denounce evil by e-mail
Question

                Recently we have discovered that some of the enemies of Islam are insulting Islam and saying bad things about the Messenger of Allaah Muhammad (peace and blessings of Allaah be upon him), either in words or in drawings – may Allaah curse them. Sometimes news of this comes to us in e-mails and the Muslims are asked to denounce these evils either by sending e-mails or by ordinary mail or by letting the evildoer know how the Muslims feel. My question is: if we do not carry out this denunciation are we sinning? Or if some people do it will the others be absolved of responsibility?.
Praise be to Allah.
    Firstly: the basic principle is that denunciation of evil is 
    a fard kafaayah (communal obligation), so if sufficient people undertake it, 
    the rest are absolved of sin. 

    Al-Nawawi (may Allaah have mercy on him) said in his 
    commentary on Saheeh Muslim: 
Enjoining what is good 
    and forbidding what is evil is fard kafaayah (communal obligation); if some 
    people do it then the rest are absolved of sin, but if no one  does it, 
    everyone who was able to do it with no excuse or fear (but did not do it) is 
    guilty of sin. But it may also be an individual obligation, such as if a 
    person is in a situation where no one else knows of it but him, or no one 
    can remove it but him, or such as if a man sees his wife, child or slave 
    committing an evil action or failing to do something good. End quote. 

    But we must not forget the obligation of enjoining what is 
    good and forbidding what is evil. The Muslims should do that, because the 
    Prophet  (peace and blessings of Allaah be upon him) said: “Whoever 
    among you sees an evil action, let him change it with his hand (by taking 
    action); if he cannot then with his tongue (by speaking out); and if he 
    cannot then with his heart (by hating it and feeling that it is wrong), and 
    that is the weakest of faith.” Narrated by Muslim, 49. 

    This becomes more important the worse the evil action is, and 
    there is no evil action worse than insulting Allaah and His religion Islam, 
    or insulting His Messenger Muhammad  (peace and blessings of Allaah be 
    upon him). 

    Whoever comes across any of these evil actions, in a 
    newspaper or magazine, or on a satellite channel or elsewhere has to 
    denounce it as much as he can, with his hand (by taking action), with his 
    tongue (by speaking out) or with his heart (by hating it), as enjoined by 
    the Prophet  (peace and blessings of Allaah be upon him). 

    Whoever does not see it or come across it, but is told of it 
    by others, should also hasten to denounce it, by getting in touch with the 
    newspaper or channel, or getting in touch with the writer of the article 
    himself, and denouncing them. If people see how many are denouncing it they 
    will be deterred from repeating the evil action, and they may even apologize 
    publicly and repent. 

    Moreover, if many people agree on denouncing an evil action, 
    that will be indicative of the power of the religious people, and their 
    protective jealousy and their awareness of what is being broadcast and 
    published. This is something that is required by sharee’ah, otherwise you 
    will find that every day someone dares to say something bad about Islam. 

    Moreover, this is a means of earning reward, for the one who 
    denounces evil will be rewarded. 

    We ask Allaah to make our religion prevail and to humiliate 
    the people of deviance and misguidance. And Allaah knows best.