GP leaders warned that patient safety could be at risk, because practices could be unable to access messages from hospital colleagues, test results and other information relevant to patient care.
GPonline reported on Monday that GPs across England were left unable to access emails after a message sent by mistake to all 840,000 NHS Mail users crashed the system used by most health service staff.
Subsequent emails complaining about the message magnified the problem as other users hit the 'reply all' option, triggering a huge spike in email traffic via NHS Mail.
GP email access
On Tuesday, as some users began to regain access to their accounts, many began the process of deleting the rogue messages - which experts believe triggered a further spike in traffic that again slowed the system down or left it inaccesible for many GPs.
GPC deputy chair Dr Richard Vautrey told GPonline on Tuesday afternoon: 'It is really, really slow. Yesterday we were bombarded by these repeat messages, so couldn't use the system in any significant way. Today, lots of the messages sent by users yesterday started to appear, and throughout the day it has been very slow getting onto the system and accessing it.
'There may well be emails and important messages users have been unable to access, sent over the past 48 hours – it's tough to know how important those are, and the impact. It's also possible information could be lost among the mass of emails sent over the past few hours.'
Dr Vautrey warned that as colleagues tried to delete the large numbers of messages that generated the NHS Mail meltdown, they 'may end up deleting other messages they need through no fault of their own'.
Bedforshire and Hertfordshire LMC deputy chair and GP IT expert Dr John Lockley told GPonline that 'hundreds of thousands of users deleting unwanted mail traffic from their accounts' on Tuesday would have added to the overall load on the NHS Mail system.
He had been unable to access his NHS Mail account on Tuesday, he said, and could not pick up messages he was expecting about medicines management.
In a comment posted on GPonline Dr Lockley wrote that while GPs were largely able to continue working, and could have made phone calls for most things they felt were urgent, NHS management was likely to have been 'totally stopped from working'.
He pointed out that the individual who sent the initial rogue message should not be blamed, and that the poor design of the system was in fact at fault.
An NHS Digital spokeswoman said on Tuesday afternoon: 'The volume of traffic on the NHS Mail system has now returned to expected levels with no significant backlog. However, we will be continuing to closely monitor the situation, particularly during periods of peak mail usage today and any residual issues identified will be addressed.
'We are currently assessing the full impact on the NHS Mail service and any onward impact this may have had on wider NHS services.'