Canon MB2100 SERIES Online Manual page 1235

3418
Cause
Communication with mail server failed.
What to Do
Press the printer's OK button.
Make sure that the settings item for the outgoing mail server (SMTP server) are correct with Remote UI.
Setting Mail Server
If the error is not resolved, check your mail server condition.
For settings and condition of your mail server, contact the administrator of mail server.
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