Magento 1.9 Checkout – Email Domain Validation

In magento checkout, if the customer's email domain is not valid, the order is normally completed, using email.example.com as custome email.

I have found that there's a list of allowed email domains in lib/Zend/Validate/Hostname.php file, but adding new domains on that list is not a solution. Shouldn't magento prevent orders using non-valid email domains? Or just display a warning in checkout page, informing customer about his email? Isn't this part of email validation?

I'd like to add a warning in checkout page, in case the email domain is not valid. How can I do that?

SOLUTION POSTED BELOW

In file js/prototype/validation.js file, replace ['validate-email'] code with the following:

['validate-email', 'Please enter a valid email address. For example johndoe@domain.com.', function (v) {
    return Validation.get('IsEmpty').test(v) || /^([a-z0-9,!\#\$%&'\*\+\/=\?\^_`\{\|\}~-]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])+(\.([a-z0-9,!\#\$%&'\*\+\/=\?\^_`\{\|\}~-]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])+)*@([a-z0-9-]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])+(\.([a-z0-9-]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])+)*\.((abogado|ac|academy|accountants|active|actor|ad|ae|aero|af|ag|agency|ai|airforce|al|allfinanz|alsace|am|an|android|ao|aq|ar|archi|army|arpa|as|asia|associates|at|attorney|au|auction|audio|autos|aw|ax|axa|az|ba|band|bar|bargains|bayern|bb|bd|be|beer|berlin|best|bf|bg|bh|bi|bid|bike|bio|biz|bj|black|blackfriday|bloomberg|blue|bm|bmw|bn|bnpparibas|bo|boo|boutique|br|brussels|bs|bt|budapest|build|builders|business|buzz|bv|bw|by|bz|bzh|ca|cab|cal|camera|camp|cacerresearch|capetown|capital|caravan|cards|care|career|careers|casa|cash|cat|catering|cc|cd|center|ceo|cern|cf|cg|ch|channel|cheap|christmas|chrome|church|ci|citic|city|ck|cl|claims|cleaning|click|clinic|clothing|club|cm|cn|co|coah|codes|coffee|college|cologne|com|community|company|computer|condos|construction|consulting|ontractors|cooking|cool|coop|country|cr|credit|creditcard|cricket|crs|cruises|cu|cuisinella|cv|cw|cx|cy|cymru|cz|dad|dance|dating|day|de|deals|degree|delivery|democrat|dental|dentist|desi|diamonds|diet|digital|direct|directory|discount|dj|dk|dm|dnp|do|domains|durban|dvag|dz|eat|ec|edu|education|ee|eg|email|emerck|energy|engineer|engineering|enterprises|equipment|er|es|esq|estate|et|eu|eus|events|everbank|exchange|expert|exposed|fail|farm|feedback|fi|finance|financial|firmdale|fish|fishing|fitness|fj|fk|flights|florist|flsmidth|fly|fm|fo|foo|forsale|foundation|fr|frl|frogans|fund|furniture|ftbol|ga|gal|gallery|gb|gbiz|gd|ge|gent|gf|gg|gh|gi|gift|gifts|gives|gl|glass|gle|global|globo|gm|gmail|gmo|gmx|gn|google|gop|gov|gp|gq|gr|graphics|gratis|green|gripe|gs|gt|gu|guide|guitars|guru|gw|gy|hamburg|haus|healthcare|help|here|hiphop|hiv|hk|hm|hn|holdings|holiday|homes|horse|host|hosting|house|how|hr|ht|hu|ibm|id|ie|il|im|immo|immobilien|in|industries|info|ing|ink|institute|insure|int|international|investments|io|iq|ir|is|it|je|jetzt|jm|jo|jobs|joburg|jp|juegos|kaufen|ke|kg|kh|ki|kim|kitchen|kiwi|km|kn|koeln|kp|kr|krd|kred|kw|ky|kz|la|lacaixa|land|lawyer|lb|lc|lds|lease|legal|lgbt|li|life|lighting|limited|limo|link|lk|loans|london|lotto|lr|ls|lt|ltda|lu|luxe|luxury|lv|ly|ma|madrid|maison|management|mango|market|marketing|mc|md|me|media|meet|melbourne|meme|memorial|menu|mg|mh|miami|mil|mini|mk|ml|mm|mn|mo|mobi|moda|moe|monash|money|mormon|mortgage|moscow|motorcycles|mov|mp|mq|mr|ms|mt|mu|museum|mv|mw|mx|my|mz|na|nagoya|name|navy|nc|ne|net|network|neustar|new|nexus|nf|ng|ngo|nhk|ni|ninja|nl|no|np|nr|nra|nrw|nu|nyc|nz|okinawa|om|ong|onl|ooo|org|organic|otsuka|ovh|pa|paris|partners|parts|party|pe|pf|pg|ph|pharmacy|photo|photography|photos|physio|pics|pictures|pink|pizza|pk|pl|place|plumbing|pm|pn|pohl|poker|post|pr|praxi|press|pro|prod|productions|prof|properties|property|ps|pt|pub|pw|py|qa|qpon|quebec|re|realtor|recipes|red|rehab|reise|reisen|reit|ren|rentals|repair|report|republican|rest|restaurant|reviews|rich|rio|rip|ro|rocks|rodeo|rs|rsvp|ru|ruhr|rw|ryukyu|sa|saarland|sarl|sb|sc|sca|scb|schmidt|schule|science|scot|sd|se|services|sexy|sg|sh|shiksha|shoes|si|singles|sj|sk|sl|sm|sn|so|social|software|sohu|solar|solutions|soy|space|spiegel|sr|st|su|supplies|supply|support|surf|surgery|suzuki|sv|sx|sy|sydney|systems|sz|taipei|tatar|tattoo|tax|tc|td|technology|tel|tf|tg|th|tienda|tips|tirol|tj|tk|tl|tm|tn|to|today|tokyo|tools|top|town|toys|tp|tr|trade|training|travel|tt|tui|tv|tw|tz|ua|ug|uk|university|uno|uol|us|uy|uz|va|vacations|vc|ve|vegas|ventures|versicherung|vet|vg|vi|viajes|villas|vision|vlaanderen|vn|vodka|vote|voting|voto|voyage|vu|wales|wang|watch|webcam|website|wed|wedding|wf|whoswho|wien|wiki|williamhill|wme|work|works|world|ws|wtc|wtf|xn--1qqw23a|xn--3bst00m|xn--3ds443g|xn--3e0b707e|xn--45brj9c|xn--45q11c|xn--4gbrim|xn--55qw42g|xn--55qx5d|xn--6frz82g|xn--6qq986b3xl|xn--80adxhks|xn--80ao21a|xn--80asehdb|xn--80aswg|xn--90a3ac|xn--c1avg|xn--cg4bki|xn--clchc0ea0b2g2a9gcd|xn--czr694b|xn--czru2d|xn--d1acj3b|xn--d1alf|xn--fiq228c5hs|xn--fiq64b|xn--fiqs8s|xn--fiqz9s|xn--flw351e|xn--fpcrj9c3d|xn--fzc2c9e2c|xn--gecrj9c|xn--h2brj9c|xn--i1b6b1a6a2e|xn--io0a7i|xn--j1amh|xn--j6w193g|xn--kprw13d|xn--kpry57d|xn--kput3i|xn--l1acc|xn--lgbbat1ad8j|xn--mgb9awbf|xn--mgba3a4f16a|xn--mgbaam7a8h|xn--mgbab2bd|xn--mgbayh7gpa|xn--mgbbh1a71e|xn--mgbc0a9azcg|xn--mgberp4a5d4ar|xn--mgbx4cd0ab|xn--ngbc5azd|xn--node|xn--nqv7f|xn--nqv7fs00ema|xn--o3cw4h|xn--ogbpf8fl|xn--p1acf|xn--p1ai|xn--pgbs0dh|xn--q9jyb4c|xn--qcka1pmc|xn--rhqv96g|xn--s9brj9c|xn--ses554g|xn--unup4y|xn--vermgensberater-ctb|xn--vermgensberatung-pwb|xn--vhquv|xn--wgbh1c|xn--wgbl6a|xn--xhq521b|xn--xkc2al3hye2a|xn--xkc2dl3a5ee0h|xn--yfro4i67o|xn--ygbi2ammx|xn--zfr164b|xxx|xyz|yachts|yandex|ye|yoga|yokohama|youtube|yt|za|zip|zm|zone|zw))$/i.test(v)
}],

I know it's not elegant, but it might help somebody out there, so I post it anyway.