Is there a limit to the size / characters of an email address value?

Environment:

Email address field in various tables, All versions

Resolution:  

Yes, there is a limit of 255 characters. Examples of where this applies are business rules, contacts.email and accounts.email.

Business Rule:
In a rule that uses a condition to send an email message, the email recipient (send to) value is limited to 255 characters.

For example, if you have a rule that includes an action "Then" statement of
choose email > email incident information
the email address value must be <= 255 characters.

Contact Email Address:
If the contact email address has more than 255 characters, the incoming message will be filtered.  The filtered message shows up in tm_filter_details table (reason: invalid address). This data can be utilized in reports. Please refer to Answer ID 5358: Filtered Rejected Emails for additional information.  

Also note that, in some cases, the From address might look ok, as it has less than 255 characters, but the Reply-to address has more than 255 characters.  The Reply-to address takes precedence over the From address and as a result, the message will get filtered. Refer to Answer ID 6677: Email address used for contacts created from email messages for additional information.