Revisiting the decay of scientific email addresses

Email is the primary method of communication with authors of scientific publications. This study sought to measure the reliability, over time, of contact email addresses from biomedical publications, particularly depending on email type. Emails were written to randomly selected email addresses from publications in MEDLINE, and email bounce rates were modeled probabilistically. The use of personal email addresses was quantified and compared to the use of other types of email addresses. Eighteen percent of authors' contact email addresses in MEDLINE were estimated to be invalid. A steadily growing share of email addresses was personal: 32% of all new email addresses in MEDLINE in 2018 were of this kind. These email addresses were less likely to be invalid than email addresses from other types of providers. While the percentage of invalid email addresses was significant, it was lower than previously estimated. Personal email addresses are taking an increasingly more important role by supplying more reliable email addresses to scientists. To mitigate the problem of invalid email addresses, institutions should provide email forwarding, scientific directories should offer the possibility of contacting authors, or scientific authors should use more stable email addresses.