I will be the first to admit that I make all kinds of assumptions when seeing an email address from someone.

https://beesbuzz.biz/code/439-Falsehoods-programmers-believe-about-email

• Everyone has an email address
• Everyone has exactly one email address
• An email address never changes
• Whenever an address does change, it’s under that user’s control
• Whenever an address does change, it’s because the user specifically requested it to happen
• Whenever an address does change, the old address will continue to work/exist
• Any one email address refers to only one single person
• Unique strings of characters all map to different addresses
• All email is hosted by a centralized system
• When email is sent to a user at a domain, it is delivered to a server whose address matches that domain
• When email is sent by a user at a domain, it is sent by a server whose address matches that domain
• All email comes from a .com, .net, .edu, or .org address
• You can filter out email based on the TLD or ccTLD from which it originates
• Having a particular ccTLD means that you prefer to receive communications in that country’s native language (for example, .fr → French)
• Email addresses only contain letters
• Email addresses only contain letters and numbers
• Email addresses only contain letters, numbers, and a handful of common punctuation marks (e.g. ., _, and -)
• Email addresses will have at least one letter in them
• An email address like ^_^@example.com or +&#@example.com is invalid
• Email is a reliable transport
• Email is an instantaneous transport
• Emails will be sent within a few minutes of their scheduling
• Emails will be sent within a few hours of their scheduling
• Emails will be sent within a few days of their scheduling
• Emails will be received soon after they’re sent
• When an email is sent it immediately goes to its destination server
• If an email bounces, the address is invalid
• If an email doesn’t bounce, the address is valid
• An address which is valid will always be valid, and an address which is invalid will always be invalid
• All email is sent via SMTP over TCP/IP port 25
• All email is sent via SMTP over TCP/IP
• All email is sent via SMTP over IP
• All email is sent via SMTP
• All email servers support the various vendor extensions by the current “everyone uses this vendor” vendor (Microsoft, Google, etc.)
• An email can only have one From: address
• The Date: header on a message is legitimate
• The Received: headers will always be no earlier than the Date: header
• All email clients support HTML attachments
• All email clients support HTML message bodies
• All email clients support MIME encoding
• Email is secure
• Encrypted email is secure
• All email is accessed via webmail
• All email is accessed via webmail or IMAP
• All email is accessed via webmail, IMAP, or POP3
• Nobody uses email anymore