Old emails suddenly notified as unread

[Android Central Question]

Galaxy Note 4: every so often my phone tells me I have unread emails (Plusnet) from weeks or months ago (currently mid-December but last year it was from about 6 months previously). Usually just one or a handful but I have had over 100 suddenly appear. They appear in chronological order and one lot will often follow on from the previous bunch. I always keep my emails up to date so am certain these are false 'unreads'

 

[B. Diddy]

Welcome to Android Central! Does your email provider have a webmail interface? If so, do the emails also show up as unread there?