TL/DR (Summary): Temporary email is here to stay, people want to use it to protect their email from spam. Webmasters should not look at an email address to judge reputation. Many people use temporary email to try new products or services, some may be your biggest fans.

Full article:

First, we need to look at why do sites want to blacklist Guerrilla Mail?

It’s most likely because they want to share or sell their email address list, and such list is not as valuable if it is filled with temporary addresses. They also want to sell you stuff later, so a temporary email address puts a stop to unscrupulous practices. Sure, there are valid reasons for why a site needs an email, but it shouldn’t be mandatory. Therefore, sites that block Guerrilla Mail domains are likely to spam you later, and it’s better not to trust them.

Another reason why a site may choose to block a temporary email address may be to deter abusers from registering an account with their site. Guerrilla Mail makes it very convenient to register a new email address. (Actually, there’s no registration!). Why should it be not convenient to get a new address? Temporary email is an evolution of email, and this one of the features that has evolved and became accepted as a standard feature of temporary email. The internet is very much rapidly evolving, and how we use services and protocols will be much different to how we use them in the future.

Should your site block Guerrilla Mail?

The rise of temporary email services has become an effective tool for deterring spammers. One side effect from this is that the ‘confirm by clicking this link‘ method has become useless and outdated  for deterring abusers. Sites that use this method would need to re-think how they accept new users in to their system. For example, It would be better if they used a score system, and allow certain features only after a certain number of points has been earned. I.e., 1 point if they added and confirmed their facebook account, 1 point if they add their twitter, allow them to post once the have earned 2 points, etc.

Besides losing trust with your users and relying on outdated methods, this is the most important reason why sites should not block Guerrilla Mail:

Our users are respectful netizens, who have been users of the internet for a quite some time and are probably  very keen on trying new websites and services. These are some of the ‘early adopters’, who are savvy about the internet and know that it’s better to use a temporary email address on sites that they have seen for the first time or are not sure about. We had feedback from our users who say that they prefer to use a temporary email address when purchasing stuff, and this can be explained why our traffic always increases around Black Friday/Cyber Monday and right in the weeks leading to Christmas.