Whats the definitive maximum size of an email address?

shawson — Tue, 01 Dec 2009 09:41:12 +0000

I’ve written lots of app’s which store email addresses, and usually go for a nvarchar(100) to store them, but thought I would find out once and for all, what the actual maximum size was- just out of curiousity.

Having googled around, I came across a couple of lengthy posts on the matter (here and here), quoting figures from various standard (which seemed to point at 320 character), then corrections to those standards by members of ICANN based on the SMTP spec and so on and so forth…

After much trawling, it seems the official answer is : 254 characters (256 including the standard <> brackets around the address)

Single Character Wildcards
Premailer — preflight for HTML e-mail
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Credit/ Debt card validation rules

shawson — Wed, 01 Jul 2009 09:53:11 +0000

Valid as of 2009, from the Barclays Business website

bin_rules_may_2009.pdf (application/pdf Object).